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Right of conquest

The right of conquest is a principle of classical under which sovereignty over territory transfers from a defeated to a victorious that has seized effective control of the territory during an armed conflict, formalized through a . This doctrine, rooted in the historical acceptance of as a legitimate instrument of policy, underpinned territorial acquisitions from ancient empires through European colonial expansions, such as the Spanish conquest of the Americas authorized by papal bulls like in 1493, which justified military subjugation of territories to impose . Historically, the right required not only military victory and but also a and subsequent via , distinguishing it from mere or , and it facilitated the redrawing of borders in treaties like (1713). Its application extended to inter-European conflicts and overseas dominions, where victors claimed legal title irrespective of the justice of the initiating war, reflecting a realist view of power determining rather than moral or prior rights. By the early , however, normative shifts began eroding its legitimacy, with the 1933 Saavedra Lamas Treaty among Latin American states explicitly rejecting conquest as a basis for territorial title. In modern , the right of conquest has been rendered obsolete and inadmissible following the prohibition of the in Article 2(4) of the UN Charter (1945) and the 1970 Declaration on Principles of , which affirm that no territorial acquisition resulting from shall be recognized. Despite this, controversies persist over legacy borders established by conquest and contemporary attempts at annexation, such as Israel's 1981 extension of to the [Golan Heights](/page/Golan Heights), which the UN Security Council deemed null and void, highlighting tensions between historical precedent and post-World War II norms against forcible change. The doctrine's decline underscores a causal shift from might-based territorial legitimacy to and consent-based frameworks, though empirical realities of practice reveal incomplete adherence, as many existing sovereignties trace origins to conquest without retroactive invalidation.

Definition and Foundations

Core Definition

The right of conquest denotes the principle in classical whereby a victorious acquires title to enemy territory through effective and subjugation during or following armed conflict. Under this , possession gained by force of arms, coupled with the defeat and inability of the prior to resist, transferred legal ownership without regard to the justice of the underlying or pre-existing territorial rights. This mode of acquisition presupposed a just framework in early formulations, evolving by the 18th and 19th centuries into a realist acceptance of conquest as validated primarily by success in battle and sustained control, irrespective of moral justification. The doctrine's operation required not mere temporary seizure but permanent annexation, often formalized through treaties of peace conceding the territory, though such instruments were secondary to the fact of conquest itself. International law treated conquest as a derivative title, extinguishing the defeated state's sovereignty while imposing obligations on the conqueror to govern the annexed population, though enforcement relied on the victor's power rather than universal adjudication. Recognized as legitimate until the mid-20th century, the principle underpinned territorial expansions across history, from Roman imperial campaigns to European colonial partitions, before renunciation in the 1945 United Nations Charter, which barred force for altering borders.

Relation to Sovereignty and Territory Acquisition

The right of conquest served as a foundational mechanism for acquiring sovereignty over territory in classical international law, enabling a victorious belligerent to annex enemy land through military subjugation and establish permanent title thereto. This process transferred full sovereign authority from the defeated state to the conqueror, contingent upon effective occupation post-hostilities, which demonstrated the victor's capacity to exercise exclusive control and exclude rival claims. Unlike provisional belligerent occupation during active warfare, which preserved the occupied state's underlying sovereignty, conquest culminated in annexation, thereby extinguishing prior rights and integrating the territory into the conqueror's domain. Valid acquisition via conquest presupposed a formal declaration of war or equivalent state of hostilities, decisive military victory, and typically a peace treaty formalizing the cession, as recognition by other states reinforced the new sovereign's title. For instance, treaties such as the 1713 Treaty of Utrecht exemplified how coerced concessions in peace settlements legitimated conquest-derived sovereignty among European powers. This mode aligned sovereignty with empirical control rather than abstract consent, positing that the ability to conquer and hold territory evidenced the de facto authority essential to statehood. Among traditional modes of territorial acquisition—cession by , effective occupation of , accretion through natural processes, prescription via long , and —the latter uniquely relied on forcible displacement of an existing sovereign, underscoring power dynamics in interstate relations. 's legitimacy derived from the absence of prohibitive norms prior to the , when wars were not inherently illicit and territorial gains from them were routinely upheld. Regional restrictions emerged in the , such as in the via doctrines like the , but global acceptance persisted until the post-World War II era. Under modern , conquest no longer confers , as Article 2(4) of the 1945 UN Charter prohibits the threat or use of force against , rendering forcible acquisitions invalid and unrecognized. This shift prioritizes consensual modes like and principles, as affirmed in UN General Assembly Resolution 2625 (1970), though historical precedents continue to influence boundary disputes where pre-1945 conquests underpin existing sovereignties.

Distinctions from Other Legal Modes

The , historically recognized in as a mode of territorial acquisition, fundamentally differs from other legal mechanisms by relying on the forcible subjugation of an existing entity through military victory, followed by and effective control. Unlike consensual transfers, it presupposes the defeat and incapacity of the prior holder to resist, transferring via the victor's unilateral assertion rather than mutual . This mode was codified in treatises such as de Vattel's (1758), which distinguished conquest from mere temporary occupation by emphasizing permanent title acquisition post-war. In contrast to cession, which involves voluntary relinquishment of territory by treaty—such as the 1803 Louisiana Purchase where France transferred 828,000 square miles to the United States for $15 million—conquest entails no such negotiation or compensation, deriving legitimacy from the raw exercise of power over a defeated adversary. Cession preserves the transferring state's agency and often includes stipulations for inhabitants or boundaries, whereas conquest typically overrides prior legal orders without regard for consent, as seen in the Roman Empire's expansions where defeated kings' domains were absorbed outright. Conquest also stands apart from effective , applicable only to (land belonging to no one), requiring intent to possess and actual administration without opposition from an organized state. For instance, European claims over uninhabited Pacific islands in the relied on occupation via flags and proclamations, not ; conquest, by definition, targets territories under effective sovereign control, necessitating military overthrow to establish title, as in the Mongol invasions that subjugated populated kingdoms rather than vacant lands. Prescription, another non-forcible mode, involves gaining title through prolonged, uninterrupted, and peaceful possession—often decades or centuries—where the original owner's protests lapse into , exemplified by longstanding border adjustments in prior to formal treaties. Conquest accelerates this process violently, bypassing temporal requirements and public tranquility; it demands immediate post-battle , not gradual consolidation, and historically invalidated prior claims through the victor's dominance rather than the passage of time eroding them. Adjudication or , resolved through international tribunals like the Permanent Court of Arbitration's 1899 Alaska boundary case, relies on legal argumentation and evidence rather than arms, producing binding decisions enforceable by diplomatic pressure or collective sanction. Conquest eschews such impartial processes, substituting battlefield outcomes for judicial ones, where the stronger party's success confers title without third-party validation—a distinction rooted in realist assessments of power disparities over normative equity. Accretion, a derivative mode via natural phenomena such as alluvial deposits forming new landmasses (e.g., the 1836 between the U.S. and ), operates passively without human agency or conflict, attaching incrementally to existing frontiers. Conquest, conversely, is an active, intervention disrupting established boundaries through conquest's inherent disruption of , not environmental inevitability. These distinctions underscore conquest's unique foundation in coercive , diverging from the , passivity, or longevity characterizing alternatives.

Historical Evolution

Ancient and Pre-Modern Periods

In the , military conquest served as the foundational means for establishing over territories, with victors asserting control through direct and administrative integration. The under (c. 2334–2279 BC) marked an early instance, as Sargon subjugated city-states, unifying under a single ruler who claimed divine authority to rule the conquered regions as an integrated domain. This pattern persisted in the (911–609 BC), where kings like and conducted systematic campaigns, expanding from core territories to encompass , , , and parts of , with enforced via provincial governors, systems, and mass deportations to break local resistance and foster loyalty. Assyrian royal inscriptions portrayed these conquests as mandated by the god , blending military dominance with religious legitimacy to justify permanent territorial acquisition. The Achaemenid Persian Empire exemplified conquest's role in imperial expansion while adapting administration to sustain rule. (r. 559–530 BC) conquered the Median Empire, (546 BC), and (539 BC), incorporating diverse lands into a satrapal system where local elites retained customs under Persian oversight, yet ultimate sovereignty resided with the king as representative of . Darius I (r. 522–486 BC) further consolidated this through infrastructure like the Royal Road and standardized coinage, demonstrating how conquest-derived authority enabled governance over 5.5 million square kilometers. Alexander the Great's subsequent conquest of Persia (334–330 BC) transferred sovereignty to Macedonian successors, who divided the realm into Hellenistic kingdoms, ruling as divine kings over former Persian domains based on battlefield victories. Roman practice formalized conquest as a legal mode of territorial acquisition within the framework of jus gentium. From the third century BC, the annexed , , and Iberian territories post-victory, transforming defeated polities into provinces under senatorial oversight, with sovereignty vesting in the via laws like the Lex Provinciæ. Jurists emphasized bellum justum—wars initiated for legitimate causes like reparations or defense—but effective occupation after victory conferred title, as reflected in later codifications like the Digest of Justinian (533 AD), which upheld enemy property as spoils. This approach underpinned the Empire's control over 5 million square kilometers by the second century AD, where conquest not only expanded borders but integrated economies through taxation and grants. In pre-modern contexts up to , such as Byzantine reconquests or early Islamic expansions (e.g., Caliphate's conquests from 632–661 AD), military success continued to legitimize , often invoking divine will alongside pragmatic administration to maintain conquered territories.

Medieval to Enlightenment Era

In medieval Europe, military conquest served as a de facto mechanism for territorial acquisition, often legitimized through feudal customs and religious authority rather than a codified universal right. The of in 1066 exemplifies this, as Duke William of Normandy, after defeating King Harold II at the on October 14, claimed the English throne based on a mix of alleged promises and papal endorsement, but solidified rule through redistribution of approximately 4,000 manors to over 180 Norman tenants-in-chief, effectively basing on possession maintained by force. Similarly, the , a series of campaigns from the in 722 to the capture of on January 2, 1492, enabled Christian kingdoms like and to reclaim Iberian territories from Muslim control, justified as restoration of pre-Islamic Christian dominion and supported by papal indulgences that equated conquest with holy war. Scholastic theology provided intellectual underpinnings, with (c. 1225–1274) outlining just war criteria in (II-II, q. 40): authority from a sovereign, just cause such as punishing wrongdoing or recovering seized goods, and right intention aimed at peace rather than private gain. While Aquinas did not explicitly endorse unlimited conquest, his framework permitted victors to retain conquered lands as recompense for injuries, influencing practices where effective control trumped prior titles unless challenged successfully. This realist approach aligned with feudal realities, where lords' rights derived from conquest or grant, as seen in the Carolingian expansions under (r. 768–814), who subdued Saxon tribes between 772 and 804, annexing their lands into the Frankish Empire through repeated campaigns and forced conversions. The transition to the Enlightenment saw the right of conquest secularized within emerging international law frameworks. Hugo Grotius (1583–1645), in De Jure Belli ac Pacis (1625, Book III, Chapter VIII), posited that just wars entitled victors to succeed to the full rights of the defeated sovereign, including dominion over territory and subjects, provided the war addressed prior violations of natural rights; he cited Roman precedents like the Samnite wars to argue conquest as a lawful transfer of property in extremis. Building on Grotius and Christian Wolff, Emer de Vattel (1714–1767) in The Law of Nations (1758, Book III, Chapter XIII) refined this by requiring not only a just cause—such as defensive response or punishment of aggression—but also effective occupation and subjugation of inhabitants to perfect title, rejecting conquest for mere territorial ambition as contrary to the society of nations. Vattel's principles, influential in European diplomacy, emphasized that imperfect rights from initial victory matured only through stable possession, reflecting a causal shift toward state-centric realism over medieval religious mandates. This evolution underscored conquest's role in sovereignty acquisition while imposing natural law constraints, paving the way for 18th-century balance-of-power politics.

19th and Early 20th Centuries

In the , the right of conquest persisted as a legitimate mechanism for territorial acquisition in , allowing victorious states to annex enemy territory following a formal and establishment of effective control. This principle, rooted in earlier doctrines, was routinely invoked in treaties concluding conflicts, where transferred from the defeated to the victor without requiring additional moral justifications beyond military success. powers and emerging states alike applied it during expansions, often blending conquest with claims of or , though empirical outcomes hinged on superior rather than legal niceties. The Mexican-American War (1846–1848) exemplified this practice, as forces defeated , leading to the on February 2, 1848, by which ceded approximately 525,000 square miles of territory—including present-day , , , and parts of , , , and —for $15 million. This annexation, doubling the U.S. land area, was justified under the right of conquest, with the U.S. authorizing the war and the treaty formalizing gains from battlefield victories. Similarly, the (1870–1871) resulted in annexing Alsace-Lorraine, comprising about 5,000 square miles and 1.6 million people, via the Treaty of Frankfurt, reinforcing conquest as a tool for unifying German states under Prussian leadership. The late 19th-century saw European states partition the continent through military campaigns, with conquering territories like (1882) and (1898), annexing vast swathes in West and , and under King Leopold II seizing the via force after 1885. The (1884–1885) regulated claims but did not prohibit , instead facilitating divisions based on effective , which often required armed subjugation of local resistances; by 1914, European powers controlled 90% of Africa's landmass. These acquisitions underscored causal realism in , where industrial military advantages enabled dominance, overriding claims. Into the early 20th century, the (1904–1905) demonstrated non-European application, with Japan's victory yielding the , granting control of , the , southern Island, and paramount influence over —territorial gains explicitly recognized by great powers as fruits of conquest. Italy's (1911–1912) led to annexation of and the Dodecanese Islands, while the (1912–1913) enabled , , , and to conquer and partition Ottoman-held territories in . Even as humanitarian critiques emerged, such as anti-slavery campaigns masking , the legal framework upheld conquest until the Kellogg-Briand Pact of 1928 began eroding it by renouncing aggressive war, though violations persisted without invalidating prior norms. This era's practices reflected power asymmetries, with conquest enabling empire-building until interwar normative shifts.

Theoretical and Legal Arguments

Justifications from Realist and Power-Based Perspectives

In , the anarchic structure of the global system—lacking a sovereign authority to enforce rules—compels states to pursue power as the primary means of survival and security, rendering a rational instrument for acquiring territory, resources, and strategic advantages when power asymmetries permit. This perspective prioritizes empirical observations of state behavior over normative ideals, viewing not as inherently moral but as an effective response to the perpetual competition inherent in and interstate rivalry. Thucydides' provides a foundational illustration through the Melian Dialogue of 416 BCE, where Athenian representatives reject appeals to or neutrality, asserting that "the strong do what they can and the weak suffer what they must," thereby justifying subjugation of the neutral island of Melos to consolidate imperial power and deter rebellion. This exchange underscores the realist axiom that power, rather than ethical claims, determines outcomes in conflicts, with serving as the mechanism to translate military superiority into enduring control. Niccolò , in (1532), extends this logic to statecraft, contending that new principalities frequently arise from and that rulers must seize opportunities for expansion through force, as stable orders trace back to violent origins that fortune and enable. He advises princes to prioritize effective possession over legalistic pretensions, arguing that fosters unity and resilience against internal decay, with historical expansions exemplifying how aggressive acquisition prevented stagnation. Thomas Hobbes, in Leviathan (1651), formalizes conquest as a valid path to , distinguishing "sovereignty by acquisition" from consensual , where a conqueror secures absolute authority by subduing subjects who, fearing death, submit and thereby legitimize the ruler's dominion akin to a enforced by coercion. Hobbes posits that such arrangements avert the natural state of war, with the conqueror's unchallenged power ensuring peace, as empirical history shows conquered peoples transferring to avoid . Hans Morgenthau's , articulated in (1948), frames interstate politics as an unrelenting struggle for , where —defined as deliberate efforts to overturn the for dominance—emerges from states' rational calculation of interests, validating as a tool for balancing or augmenting capabilities against rivals. Morgenthau observes that such policies, while risking overextension, align with the empirical reality of vacuums filled by forceful expansion, as seen in historical bids for that reshaped territorial distributions. From this view, denying conquest's efficacy ignores causal dynamics where superior military and economic might compels recognition of new realities, sustaining the balance of over idealistic prohibitions.

Moral and Ethical Defenses

Moral and ethical defenses of the right of conquest have historically drawn from traditions, positing that victorious powers in lawful wars acquire legitimate dominion as a means to restore order, punish aggression, or secure enduring peace. , in (1625), argued that the law of nature permits conquerors to rule over the defeated as they see fit, provided the war was just, citing precedents like the acceptance of such outcomes to prevent endless reprisals and stabilize relations. This view frames conquest not as mere predation but as a resolution mechanism inherent to human conflict, where submission to the victor averts the chaos of perpetual vendettas. Thomas Hobbes extended this reasoning in Leviathan (1651), justifying sovereignty acquired through conquest as morally equivalent to consensual forms, since it terminates the state of nature's mutual destruction by imposing absolute authority capable of enforcing peace. Hobbes contended that in the absence of a common power, individuals and states revert to self-help via force, rendering conquest a pragmatic ethical imperative for survival and civil order, as the alternative—unfettered rivalry—yields greater immorality through unchecked violence. Emer de Vattel, in The Law of Nations (1758), defended conquest in contexts of just cause, such as reclaiming property or punishing sovereigns who violate natural rights, while also endorsing territorial appropriation from uncultivated lands to promote human flourishing under superior stewardship. Vattel's framework emphasized that ethical conquest advances civilization by transferring governance to entities better able to cultivate resources and uphold justice, aligning with a utilitarian calculus where long-term societal benefits outweigh initial coercion. In realist , ethical defenses portray conquest as a reflection of causal power dynamics in an anarchic system, where denying its legitimacy invites hypocrisy and instability rather than moral progress. Proponents argue that recognizing conquest's outcomes, as in pre-20th-century European practice, provides decisive closure to disputes, preventing "frozen conflicts" perpetuated by rigid territorial sanctity without enforcement mechanisms. , in (1532), implicitly supported expansionist conquest as ethically necessary for state vitality amid inevitable flux, advising rulers to secure gains ruthlessly to avert decay, thereby prioritizing over abstract . These arguments collectively assert that conquest, when rooted in defensive or retributive wars, enforces accountability and progress, countering idealist objections by grounding ethics in observable human incentives rather than unattainable utopias.

Criticisms and Idealist Objections

Critics of the right of conquest from idealist perspectives contend that it fundamentally contravenes principles of and among peoples, positing that territorial acquisition through force equates to "," which undermines the in . Early theorists such as argued against unlimited conquest, asserting that even in cases of just war, victors could not claim dominion over defeated populations without evidence of grave offenses like persistent threats to natural rights, as seen in his critique of Spanish actions in the during the 1530s, where he emphasized the inherent of unless they violated ius gentium. Similarly, in (1625) imposed strict limits, allowing conquest only as a remedy for just causes and prohibiting excessive punishment or permanent subjugation without necessity for self-preservation, thereby subordinating raw power to ethical constraints derived from . Enlightenment philosophers extended these objections by framing conquest as incompatible with rational cosmopolitan order. , in Perpetual Peace (1795), rejected territorial gains from as a violation of republican right, advocating instead for a of free states where remains inalienable and wars of conquest are precluded to achieve enduring peace, arguing that such practices perpetuate a among nations rather than elevating them to civil condition. echoed this in The Spirit of the Laws (1748), limiting the right to conquest to defensive necessities and preservation of the conquest's security, decrying expansive empire-building as morally corrosive and prone to tyranny over subjugated peoples. These idealist views prioritize deontological —duties and independent of outcomes—over consequentialist justifications, insisting that conquest erodes human dignity by treating populations as transferable property. In modern discourse, idealist objections invoke the maxim ex injuria jus non oritur (no right arises from wrong), a principle traceable to Alberico Gentili and Grotius, which denies legitimacy to territorial claims stemming from aggressive war, as permitting otherwise would reward criminal aggression and incentivize violations of sovereignty. Ethicists like Cian O'Driscoll argue that reviving conquest rights ignores the post-1945 normative shift against it, rooted in the recognition that war's decisiveness has waned amid nuclear risks and humanitarian catastrophes, rendering such doctrines anachronistic and morally hazardous, as evidenced by ongoing conflicts in Ukraine since 2014 and Gaza, where forcible annexations provoke indefinite resistance rather than stable order. These critiques, often from liberal internationalist frameworks, emphasize self-determination and human rights as inviolable, viewing conquest as antithetical to progress toward global justice, though proponents note that absolute rejection can entrench "frozen conflicts" without viable restitution mechanisms.

Key Historical Examples

Classical Conquests

The Achaemenid Persian Empire, established by around 559 BCE, exemplified early classical conquests through systematic military expansion across the and beyond. defeated the Median Empire, under in 546 BCE, and in 539 BCE, incorporating territories spanning modern , , , and parts of into a centralized domain governed by satrapies. Legitimacy derived from effective control and administrative tolerance, as permitted local customs and religious practices among subjugated populations, contrasting with harsher precedents of mass deportation and destruction, such as the conquest of in the 7th century BCE. This approach stabilized rule by framing conquest as a transfer of sovereignty via superior force rather than divine punishment alone. Macedonian forces under III, ascending the throne in 336 BCE, accelerated conquest dynamics by overthrowing Persian dominance and claiming vast new domains. In 334 BCE, Alexander crossed the Hellespont with approximately 48,500 troops, ritually hurling a spear into Asian soil to proclaim the continent "spear-won" territory, a symbolic assertion of ownership through martial prowess rooted in Homeric ideals. Victories at Granicus, Issus (333 BCE), and Gaugamela (331 BCE) dismantled the Achaemenid structure, enabling annexation of Persia proper, (where he was crowned ), , and regions to the Indus Valley by 326 BCE. Upon Alexander's death in 323 BCE, his generals partitioned the empire into Hellenistic kingdoms, perpetuating conquest-based titles without centralized inheritance, as de facto possession trumped prior claims. Roman expansion from the 4th century BCE onward institutionalized conquest as a pathway to imperium, integrating defeated lands through provincialization and citizenship extensions. The subjugation of by 264 BCE, followed by against (264–146 BCE) yielding North African provinces, and eastern campaigns annexing (168 BCE) and Asia Minor, rested on the principle that victories in bellum iustum—wars declared by the for defense, revenge, or alliance enforcement—conferred proprietary rights. jurists, drawing from ius gentium, viewed successful subjugation as transferring sovereignty, often justified retrospectively as disseminating pax Romana, law, and infrastructure to "barbarian" regions, though underlying drivers included resource extraction and security buffers. This framework persisted into the Empire, with emperors like adding in 106 CE via total military dominance.

Colonial and Imperial Expansions

colonial expansions from the 15th to 19th centuries exemplified the application of as a recognized mode of territorial acquisition under prevailing international legal norms, whereby victorious powers gained sovereign title over defeated territories through military subjugation. This doctrine, rooted in and elaborated by early modern jurists like , permitted the annexation of lands from non- polities deemed insufficiently sovereign or Christian, often combining force with papal or royal grants. 's validity hinged on effective control and subjugation, distinguishing it from mere , which required subsequent to confer title. The Spanish Empire's conquests in the provided paradigmatic cases, initiated after Christopher Columbus's voyages in 1492 and formalized by papal bulls such as (May 4, 1493), which authorized Spain's exclusive right to conquer and evangelize non-Christian territories west of a . Hernán Cortés's campaign against the (1519–1521) resulted in the fall of Tenochtitlán on August 13, 1521, yielding as a ; similarly, Francisco Pizarro's forces captured Inca Emperor in 1532, leading to the conquest of by 1533 and the establishment of extensive colonial holdings spanning over 13 million square kilometers by the late . These acquisitions were ratified by treaties among European powers, such as the (1494), implicitly acknowledging conquest's role in title transfer absent third-party recognition of indigenous sovereignty. British imperial expansion in India relied on incremental conquests by the , beginning with the (June 23, 1757), where Robert Clive's victory over Bengal's Nawab secured Company control over a revenue-yielding territory of approximately 120,000 square kilometers. Subsequent wars, including against the Marathas (1775–1818) and (1767–1799), expanded British dominion to over 2 million square kilometers by 1857, justified under doctrines of subsidiary alliances and lapse, which masked underlying military coercion as legal cession while conquest provided the foundational title. French and Dutch efforts paralleled this, with conquering starting in 1830 through sustained military campaigns that subdued local resistance by 1847, annexing 2.4 million square kilometers under the terra nullius pretext supplemented by conquest. The late 19th-century intensified conquest's application, as European states partitioned the continent at the (1884–1885), requiring "effective occupation" but predicated on military subjugation to assert claims over 90% of Africa's 30 million square kilometers by 1914. Belgium's King Leopold II, for instance, claimed the (2.3 million square kilometers) via private conquest forces that suppressed indigenous forces by 1908, transferring it to Belgian sovereignty after international recognition of control. These expansions underscored conquest's empirical basis in power disparities—European technological superiority in firearms and logistics enabling rapid territorial gains—while contemporaneous legal scholarship, such as Emer de Vattel's (1758), upheld it as lawful against polities lacking stable governance. Despite humanitarian critiques emerging by the 1890s, conquest retained normative legitimacy until eroded its acceptance.

World Wars and Immediate Aftermath

During , belligerents on both sides pursued territorial conquests as a legitimate wartime objective, with the occupying significant Russian, Romanian, and Serbian territories by 1918, while the Allies advanced into Ottoman and German-held areas. Post-armistice settlements, such as the signed on June 28, 1919, redistributed approximately 13% of Germany's pre-war territory—including Alsace-Lorraine to France and the to the newly independent —effectively validating conquest by the victors under the framework of national rather than pure annexation rights. However, the Covenant of the League of Nations, incorporated into the , introduced Article 10, which pledged members to "respect and preserve as against external aggression the and existing political independence of all Members," marking an early normative challenge to unfettered conquest despite ongoing imperial redistributions like the mandate system for former German and Ottoman colonies. The accelerated the doctrinal erosion of conquest through instruments like the Kellogg-Briand Pact, ratified by 63 nations on August 27, 1928, which renounced "war as an instrument of national policy" and rendered forcible territorial acquisition illegitimate, though it lacked enforcement mechanisms. This principle faced immediate tests: Japan's invasion and annexation of in September 1931 prompted U.S. Secretary of State Henry Stimson's doctrine of non-recognition on January 7, 1932, refusing to acknowledge territorial changes achieved by aggression, a policy echoed by the League of Nations' condemning the act. Italy's conquest of in 1935 similarly drew formal League sanctions but incomplete enforcement, highlighting the pact's aspirational limits while establishing non-recognition as a growing customary barrier to conquest legitimacy. World War II epitomized aggressive conquest on a massive scale, with Nazi Germany's policy justifying annexations like (March 12, 1938) and Czechoslovakia's (October 1, 1938), followed by invasions of (September 1, 1939), Denmark, Norway, and others, totaling over 1.5 million square kilometers seized by 1942. Imperial Japan's expansion into , French , and , alongside Italy's African campaigns, invoked traditional conquest rights but were framed internationally as violations of sovereignty. The Allies countered with the Atlantic Charter, announced August 14, 1941, by U.S. President and British Prime Minister , explicitly rejecting "aggrandizement, territorial or other" and affirming no territorial changes without the "freely expressed wishes of the peoples concerned," influencing subsequent declarations like the Declaration of January 1, 1942. In the immediate postwar aftermath, the International Military Tribunal (1945–1946) prosecuted 22 high-ranking Nazi officials, convicting 12 for "crimes against peace," defined as planning, initiating, or waging wars of aggression in violation of treaties like Kellogg-Briand, thereby criminalizing conquest as the "supreme international crime" distinct from mere battlefield success. The , signed June 26, 1945, and effective October 24, 1945, enshrined in Article 2(4) the obligation for members to "refrain in their from the threat or against the or political independence of any state," formally extinguishing the right of conquest as a mode of territorial acquisition under positive . Despite these developments, practical settlements like the of August 2, 1945, involved Allied zonal occupations and population transfers—such as the expulsion of 12–14 million ethnic Germans from —often rationalized through rather than conquest title, underscoring a causal shift from power-based legitimacy to normative prohibitions amid persistent geopolitical realignments.

Post-1945 International Normative Shift

Formation of Anti-Conquest Doctrines

The devastation wrought by aggressive territorial expansions during World War II prompted the Allied powers to articulate doctrines explicitly rejecting conquest as a legitimate means of altering borders. In the aftermath of the conflict, the 1945 London Agreement established the International Military Tribunal (IMT) at Nuremberg, which prosecuted Nazi leaders for "crimes against peace," defined as the planning, preparation, initiation, or waging of aggressive war or war in violation of international treaties. This indictment implicitly invalidated conquest-derived territorial claims, as the tribunal's charter equated such aggression with inherent illegality, severing the historical link between military victory and sovereign title transfer. The IMT's judgments, delivered on October 1, 1946, convicted 12 defendants of these crimes, reinforcing that forcible annexation conferred no legal rights, a principle drawn from the interwar Kellogg-Briand Pact but now enforced through retrospective criminal accountability. Parallel to Nuremberg, the doctrine of non-recognition gained doctrinal footing, mandating that states withhold diplomatic acknowledgment of territories seized by force. This built on the 1932 Stimson Doctrine—initially applied to Japan's Manchurian invasion—but was systematized post-1945 as a customary obligation, evident in Allied declarations refusing to legitimize Axis annexations such as those in , , and . U.S. and other Allied diplomats advocated this approach during wartime conferences, arguing that recognizing conquest would perpetuate instability; by 1945, it formed the basis for rejecting any post-war border changes not consensual or restorative of pre-aggression status. Scholarly analyses, such as those examining the norm's evolution, attribute its post-war formation to this non-recognition policy, which prioritized territorial ante over power-based redistribution, thereby entrenching as inviolable against force. These doctrines coalesced amid broader reflections on state sovereignty, influenced by the failures of of Nations to deter in . The , affirmed in UN General Assembly Resolution 95(I) on December 11, 1946, extended criminal liability for aggression, fostering a normative that conquest undermined the very foundations of by incentivizing endless . Empirical data from the era shows a marked decline in overt territorial conquests immediately post-1945, with states increasingly resorting to proxy conflicts or claims of rather than outright , signaling the norm's initial "compliance pull" despite lacking immediate coercive mechanisms. However, as legal scholars note, the doctrine's formation relied on the victors' , raising questions about its universality, as pre-1939 conquests (e.g., Soviet annexations) were often grandfathered rather than reversed.

UN Charter and Related Instruments

The , signed on 26 June and entering into force on 24 October 1945, established a foundational prohibition on the that effectively abolished the traditional right of conquest under . Article 2(4) mandates that "All Members shall refrain in their from the threat or against the or political of any , or in any other manner inconsistent with the Purposes of the ." This provision, rooted in the post-World War II consensus to prevent aggressive expansionism exemplified by , renders conquest—defined as the forcible acquisition and annexation of territory—as incompatible with the Charter's aims of maintaining international peace and security. Prior to , conquest had been a recognized mode of acquiring sovereignty; the Charter shifted this by prioritizing sovereign equality and territorial inviolability, though it permits force only in individual or collective under Article 51 or as authorized by the Security Council. Complementing the , 2625 (XXV), adopted on 24 October 1970 as the Declaration on Principles of concerning Friendly Relations and Co-operation among States, elaborates the non- principle to explicitly bar recognition of conquests. It states that "No territorial acquisition resulting from the threat or shall be recognized as legal," reinforcing Article 2(4) by codifying a duty of non-recognition for gains achieved through , irrespective of the occupying power's claims. This instrument, while non-binding, reflects as understood by UN member states and has been invoked in responses to post-1945 annexations, underscoring the normative rejection of conquest as a basis for title to territory. Other related frameworks, such as the 1974 Definition of (UNGA Resolution 3314), further operationalize these prohibitions by defining acts of —including or —that violate the , but they derive their authority from the core tenets of Article 2(4) and the 1970 Declaration. These instruments collectively represent the post-1945 doctrinal framework deeming conquest illegitimate, though their application hinges on interpretation and state practice rather than automatic enforcement.

Practical Enforcement and Failures

The enforcement of prohibitions against territorial acquisition by force, as codified in Article 2(4) of the UN Charter, relies primarily on the UN Security Council (UNSC) under Chapter VII, which authorizes measures ranging from economic sanctions to military intervention to maintain or restore international peace and security. This framework empowers the UNSC to determine threats to territorial integrity and impose binding resolutions, as seen in the 1990-1991 response to Iraq's invasion of Kuwait, where Resolution 678 authorized a US-led coalition to expel Iraqi forces, successfully reversing the conquest by February 1991. However, enforcement is inherently constrained by the veto power of the five permanent members (P5: United States, United Kingdom, France, Russia, Soviet Union/China), which has repeatedly paralyzed action against conquests involving P5 states or their allies. Practical failures stem from this structural veto mechanism and the absence of automatic reversal obligations, allowing consolidations of gains despite condemnations. For instance, the Soviet Union's 1940 annexations of the —initially seized via force and ultimatums—persisted post-1945 without UNSC reversal, as the USSR ed any challenges, with Western recognition withheld but no military enforcement pursued during the . Similarly, China's 1950 incorporation of through and a 1951 treaty under duress faced UN resolutions (e.g., 1959) criticizing the actions but no binding enforcement, as China (admitted to UN in ) and Soviet allies blocked UNSC measures.) Post-Cold War examples highlight selective application, often favoring weaker aggressors for enforcement while tolerating great-power violations. Indonesia's 1975 invasion and of , despite UNSC Resolution 384 calling for , endured until a 1999 and Australian-led , but only after 24 years of killing over 100,000; earlier inaction reflected veto threats and geopolitical alignments. Morocco's 1975 via the and military control prompted UNSC calls for but no reversal, with the of Justice's 1975 rejecting legal acquisition claims yet failing to compel . Russia's 2014 of followed a disputed after military ; UN Resolution 68/262 declared it invalid, but UNSC es by prevented enforcement, leaving the territory under Russian control amid ongoing sanctions without territorial restoration. These cases illustrate how enforcement succeeds against non-P5 actors with broad coalitions (e.g., ) but falters against permanent members, eroding the norm's universality—scholarly analyses count 12-18 post-1945 forcible conquests by states, many unchallenged long-term. Empirical data underscores the norm's limited deterrent effect: while overt full-state conquests declined post-1945 due to risks and alliances, partial annexations and persist, with territorial changes via force occurring in approximately 10% of post-WWII interstate wars, often without reversal. The International Criminal Court's over (activated 2018) offers prosecutorial avenues but lacks enforcement for state-level reversals, as seen in unaddressed cases like Turkey's 1974 control of . This pattern reflects causal realities of power disparities, where great powers exploit vetoes or bilateral deals, rendering anti-conquest doctrines more declarative than operative against determined actors.

Contemporary Status and Controversies

Legal Illegitimacy in Modern Doctrine

The Charter, adopted on June 26, 1945, fundamentally prohibits the acquisition of territory through the by stipulating in Article 2(4) that member states shall "refrain in their international relations from the threat or against the or political independence of any state, or in any other manner inconsistent with the Purposes of the ." This provision, interpreted as rendering conquest legally invalid for establishing sovereign title, reflects a post-World War II consensus against aggressive territorial changes, building on earlier non-recognition principles like the of 1932, which rejected Japanese gains in as illegitimate. The 1970 Declaration on Principles of International Law concerning Friendly Relations and Co-operation among States, adopted by UN General Assembly Resolution 2625 (XXV) on October 24, 1970, explicitly codifies this illegitimacy, stating that "the territory of a State shall not be the object of acquisition by another State resulting from the threat or use of force" and that "no territorial acquisition resulting from the threat or use of force shall be recognized as legal." This declaration, regarded as reflective of , reinforces the Charter's norm by emphasizing non-recognition as a duty incumbent on all states, thereby denying legal effect to conquests irrespective of effective control or passage of time. The (ICJ) has repeatedly affirmed this doctrine in s, characterizing the prohibition on acquiring territory by force as a (jus cogens) from which no derogation is permitted. In its 2004 on the Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, the ICJ held that 's security barrier in occupied areas contravened due to the underlying unlawful acquisition. More recently, in its July 19, 2024, on the Legal Consequences arising from the Policies and Practices of in the Occupied Palestinian Territory, the Court reiterated that such violations breach the prohibition on forcible acquisition, obligating states to non-recognition and non-assistance. These rulings underscore that modern doctrine treats conquest not merely as immoral but as producing null titles, with remedies including restitution where feasible, though practical application remains contested.

Empirical Challenges in Recent Conflicts

Russia's full-scale invasion of on February 24, 2022, exemplified empirical defiance of the post-1945 on conquest, as annexed approximately 18% of Ukrainian territory—including (seized in 2014), , , , and —through and sham referenda. Despite near-universal condemnation by the UN (resolution ES-11/1, March 2, 2022, adopted 141-5) affirming 's territorial integrity under Article 2(4) of the UN Charter, retained de facto control over these areas as of October 2025, bolstered by demographic engineering via forced deportations (over 1.6 million civilians, per UN estimates) and settlement of Russian nationals. This outcome underscores enforcement asymmetries: while sanctions and to (totaling $100+ billion from Western states) slowed advances, they failed to compel territorial restitution, revealing the norm's dependence on victors' restraint rather than inherent legal compulsion. In the Nagorno-Karabakh region, Azerbaijan's military offensive from September 19-20, 2023, rapidly conquered the Armenian-populated enclave, ending the self-declared and displacing nearly 100,000 ethnic (over 99% of the population) in what framed as restoring sovereignty over internationally recognized territory. Prior gains in the 2020 Second Karabakh War had already shifted control, with recapturing and surrounding districts using Turkish-supplied drones, but the 2023 operation faced minimal international pushback— statements urged restraint without enforcement, and , as Minsk Group co-chair, abstained due to its Ukraine commitments. By November 2023, integrated the region, rejecting right-of-return guarantees amid reports of cultural erasure, illustrating how resource-backed powers ('s oil revenues exceeding $20 billion annually) can consolidate conquests absent unified great-power opposition. Israel's expansion of settlements in the , with 22 new approvals announced May 29, 2025—the largest in decades—further tests the norm, as over 700,000 settlers now inhabit areas captured in the 1967 , fragmenting Palestinian contiguity and enabling annexation. The UN Security Council ( 2334, December 23, 2016) deems these illegal under the Fourth Convention's prohibition on into occupied territory, yet Israel's government, citing biblical claims and security needs, advanced plans for 12,855 new units in 2024 alone, per monitoring. In , post-October 7, 2023, operations have secured buffer zones and corridors, with proposals for long-term Israeli control raising expulsion concerns, despite ICJ provisional measures (January 26, 2024) ordering prevention of and preservation of territory. Enforcement remains rhetorical, with U.S. vetoes shielding (e.g., 14 UNSC vetoes since 1972), highlighting selective application tied to alliance dynamics rather than universal principle. China's militarization of the , including construction on seven Spratly reefs since 2013 (expanding 3,200 acres with airstrips and missiles), has effectively conquered disputed features despite the 2016 ruling invalidating Beijing's "" claims. and the protested incursions—such as the 1988 clash and 2023 clashes damaging Philippine vessels—but China's patrols ensure dominance, with no reversals enforced by or the U.S. beyond freedom-of-navigation operations. This "salami-slicing" strategy, yielding control over $3.4 trillion in annual trade routes, empirically prioritizes possession over legal title, as smaller claimants lack capacity for sustained resistance. These cases reveal a pattern: while doctrinal instruments like the UN Charter proscribe conquest, empirical outcomes favor the militarily superior actor's retention of gains, with reversals (e.g., Iraq's 1991 Kuwait withdrawal) occurring only against defeated non-nuclear powers lacking veto-wielding patrons. Dissenting analyses, such as Russian legal justifications invoking "" or Azerbaijani assertions of historical rights, gain traction domestically but falter internationally, yet territorial facts endure, challenging the norm's purported absoluteness.

Debates on Revival and Hypocrisy in Application

In scholarship, debates on reviving the right of conquest center on whether the post-1945 taboo against territorial acquisition by force remains viable amid repeated violations, or if pragmatic acceptance of faits accomplis could resolve protracted conflicts more effectively than indefinite resistance. Realist analysts contend that in an anarchic global system, conquest reflects power dynamics, and rigid non-recognition prolongs instability, as evidenced by Russia's 2014 annexation of and 2022 seizures in Ukraine's , , , and oblasts following referendums rejected by and most Western states. Some U.S. data from 2023-2024 shows increasing support for negotiating territorial concessions to to halt fighting, particularly among respondents, arguing that denying conquest outright ignores military realities and risks escalation. Opponents, however, assert that revival would erode deterrence, citing Azerbaijan's 2023 military operation reclaiming from as a that could encourage revisionist powers like toward . Historical precedents underscore moral tensions in any revival, as early modern theorists like and viewed conquest as conferring legal title to ensure wars yielded decisive outcomes, regardless of initial justice, but this framework clashes with contemporary prohibitions under the UN Charter's Article 2(4), which bans force altering . In , Russia's claims rest on asserted historical ties and security needs, while in , Israel's post-2023 Hamas war plans for prolonged military presence raise parallels to control without formal , prompting ethicists to warn that endorsing for "just" victors revives a "might makes right" ethos incompatible with norms and likely to perpetuate cycles of retaliation. These debates highlight causal realism: without credible enforcement, norms decay, but revival risks legitimizing aggression over defensive wars. Hypocrisy charges dominate critiques of norm application, with non-Western states and scholars pointing to Western selectivity that privileges allies while condemning adversaries. For instance, the U.S. and allies recognized Kosovo's 2008 independence—following the 1999 intervention that altered Serbia's borders without UN Security Council approval—yet refuse to acknowledge Crimea's 2014 status despite a similar plebiscite, a invoked by Russian officials to justify their actions. Legal scholar Ben Saul argues this inconsistency, including Western tolerance for interventions like the 2003 invasion (framed as rather than conquest), erodes global adherence to rules, as non-Western powers perceive the order as power-serving rather than universal. Further, U.S. criticism of arrest warrants for Russian leaders contrasts with opposition to warrants against Israeli officials in the context, fueling accusations from Global South observers that enforcement hinges on geopolitical alignment rather than principle. Such disparities, Saul contends, embolden aggressors by signaling norms as optional for the powerful, though Western defenders counter that consistent condemnation of unprovoked invasions like Ukraine's upholds the more than selective lapses undermine it.

Broader Implications

For State Formation and Legitimacy

The formation of states throughout history has frequently occurred through , whereby a conquering entity establishes over and populations by force, supplanting prior political orders with effective control and governance structures. This process, encapsulated in the of origin, posits that dominant groups impose authority on subjugated ones, creating centralized polities through military dominance rather than . Empirical analyses of pre-modern indicate that such formations, spanning empires like the or Mongol, derived legitimacy from sustained administrative control and the inability of defeated parties to reclaim , fostering long-term stability when conquerors integrated economic exploitation and defensive capabilities. For instance, historical data on agrarian states show that conquest-driven expansions often persisted due to the victor's capacity to prevent reversal, with accumulated experience over millennia correlating positively with political stability in successor entities. Philosophically, legitimacy under conquest contrasted with consent-based theories by grounding authority in demonstrable power rather than hypothetical agreement, as critiqued by thinkers like who noted the absence of actual consent in state origins, rendering social contract fictions implausible for historical polities. In practice, conquered territories gained de facto legitimacy through the conqueror's provision of order, security, and resource allocation, which empirically reduced internal fragmentation compared to stateless or contested zones. This causal mechanism—where military success enabled institutional consolidation—underpinned the vast majority of enduring states prior to the , with borders often tracing to wartime outcomes rather than indigenous . In the , the post-1945 normative rejection of has decoupled state legitimacy from forcible acquisition, emphasizing instead principles, , and international for territorial integrity. However, this shift creates tensions for , as legitimacy now hinges on diplomatic consensus rather than effective control, complicating for entities arising from , such as post-colonial breakaways or disputed annexations. Empirical trends post-World War II reveal a decline in successful territorial conquests, with fewer than 10% of militarized disputes resulting in enduring annexations after 1975, attributed to enforcement norms that prioritize pre-existing borders over outcomes. Consequently, many contemporary states inherit legitimacy from historical conquests solidified before the norm's entrenchment, yet face challenges in adapting to power shifts, as unrecognized conquests undermine formal while governance persists in stable cases. This duality highlights a selective application: pre-20th-century conquests underpin stable legitimacy, whereas modern attempts invite isolation, potentially incentivizing indirect influence over overt formation.

Causal Role in Civilization and Security

The right of conquest facilitated the formation of expansive polities capable of monopolizing violence within their territories, thereby establishing that enabled and cultural development. Empirical studies demonstrate that technologies enabling conquest, such as , had a causal on long-term state centralization and institutional strength, reducing fragmentation and chronic intertribal warfare that plagued pre-conquest societies. Larger states emerging from conquest absorbed weaker entities, creating hierarchies where rulers provided protection in exchange for , fostering stability essential for , , and . This dynamic shifted societies from constant low-level conflict to structured , allowing resources to be redirected toward advancements in and rather than perpetual defense. In the Roman case, successive conquests from the BCE onward unified diverse regions under a single legal and military framework, spreading engineering feats like aqueducts and roads that sustained urban centers and facilitated commerce. The , spanning roughly 200 years from 27 BCE to 180 CE, exemplified how conquest-enforced security minimized border threats and internal strife, permitting intellectual pursuits in , , and that influenced subsequent Western civilization. Conquered provinces benefited from extensions and infrastructure investments, which integrated local economies into an imperial system promoting technological diffusion, such as improved water management and military logistics adapted for civilian use. Similarly, under from 1206 CE consolidated nomadic tribes into an empire spanning Eurasia, enforcing the that secured routes like the , boosting cultural exchange and technological transfers including , , and navigational tools. This era's stability reduced banditry and tolls, enabling merchants to traverse vast distances safely and accelerating the spread of ideas and innovations across continents. Defensive crusades in the , while not pure conquest, similarly spurred state consolidation in by necessitating centralized , which correlated with increased , volumes, and transitions from feudal fragmentation to proto-modern states. Overall, the right of conquest acted as a Darwinian selector, rewarding polities with superior and , which in turn propagated civilizational progress through enforced and pooling. Without this , persistent multipolarity among small entities historically led to higher violence rates and stalled development, as evidenced by pre-imperial Europe's tribal skirmishes versus imperial eras' relative security. This causal chain underscores conquest's role in scaling human cooperation beyond , underpinning the security preconditions for complex societies.

Future Prospects Amid Power Shifts

As U.S. relative military and economic dominance wanes—evidenced by China's GDP surpassing 70% of the U.S. total in purchasing power parity terms by 2023 and Russia's demonstrated resilience in Ukraine despite sanctions—the post-World War II norm against territorial conquest faces erosion in a multipolar environment. Revisionist powers like China and Russia, unbound by the same liberal institutional constraints, exploit enforcement gaps in bodies like the United Nations, where Security Council vetoes shield aggressors from binding resolutions. Russia's 2014 annexation of Crimea and 2022 seizures in Ukraine, retaining control over approximately 18% of Ukrainian territory as of 2025 despite international condemnation, illustrate how power asymmetries enable de facto conquest without formal doctrinal revival, signaling to observers like Beijing that possession can confer legitimacy if held long enough. Prospects for normalized conquest sharpen around flashpoints like , where 's conducted over 1,700 aircraft incursions into Taiwan's air defense zone in 2024 alone, testing resolve amid U.S. commitments strained by domestic fiscal pressures and overstretch. Analysts from institutions like the Endowment project that a U.S.- geopolitical bargain might tacitly cede spheres of influence, potentially legitimizing Chinese control over if military faits accomplis outpace diplomatic backlash, as Ukraine's protracted defense has not reversed gains. This dynamic echoes historical patterns where declining hegemons' inability to project power—U.S. defense spending as a share of global totals dropping from 40% in 2000 to under 35% by 2025—invites opportunistic expansion, undermining Article 2(4) of the UN Charter's prohibition on force for territorial change. In a truly multipolar order, the causal logic of 's revival stems from reduced deterrence: without a singular , bilateral power balances favor the strong, as seen in China's "no-limits" partnership with enabling mutual and swaps that bolster both against Western isolation. European security analyses warn that unchecked Sino-Russian alignment could cascade into broader acceptance of , with Taiwan's fate serving as a —if unresolved by 2030, it may normalize hybrid annexations elsewhere, reverting toward realist equilibria where effective control trumps legal title. Counterarguments positing stabilized multipolarity through pragmatic alliances overlook empirical precedents, such as the and Austro-Hungarian empires' collapses amid power diffusion, which precipitated rather than prevented aggressive redrawings.