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Ansei

Ansei (安政, "Peaceful Politics") was the nengō, or era name, of Japan spanning from November 1854 to March 1860, during the reign of Emperor Kōmei amid the late Edo period's transition toward the Bakumatsu.^[1] The era commenced shortly after Commodore Matthew Perry's coerced opening of Japanese ports to U.S. trade, ushering in unequal treaties with Western powers that eroded sakoku isolationism and fueled domestic unrest.^[2] It was defined by catastrophic natural disasters, notably the Ansei great earthquakes—a series of megathrust events including the Ansei Nankai (magnitude 8.4, December 1854), Ansei Tōkai, and Ansei Edo quakes (November 1855, magnitude ~7.0)—which devastated coastal regions, killed tens of thousands, and prompted urban reconstruction in Edo (modern Tokyo) while exposing infrastructural vulnerabilities.^[1]^[2] Politically, the period saw the Ansei Purge (1858–1860), a shogunal crackdown led by Tairo Ii Naosuke targeting imperial loyalists and sonnō jōi advocates opposed to foreign influence, resulting in executions, imprisonments, and suppression of dissent to enforce the Harris Treaty and centralize Tokugawa authority.^[3] These tensions culminated in Ii's assassination at Sakuradamon Gate in 1860, signaling the purge's backlash and accelerating shogunal decline.^[4] Economically, Ansei reforms included debasing silver coinage to address fiscal strains from indemnities and military buildup, though this spurred inflation.^[5]

Chronology and Naming

Adoption of the Era Name

The Ansei era name (安政), meaning "peaceful administration" or "tranquil governance," was adopted on November 15, 1854, corresponding to the 27th day of the 10th month in the seventh year of Kaei (Kaei 7/10/27), marking the end of the preceding Kaei era.^[6] This change occurred amid a period of domestic instability, including the recent arrival of U.S. Commodore Matthew Perry's "Black Ships" in 1853–1854, which pressured Japan's isolationist policies, though the immediate catalyst was a major fire that engulfed the Kyoto Imperial Palace on July 20, 1854 (Kaei 7/7/23).^[7] The blaze destroyed the palace complex, including key structures like the Shishinden audience hall, necessitating urgent reconstruction that began the following year.^[7] The selection of "Ansei" drew from classical Chinese texts and aphorisms emphasizing stable rule, as was customary for nengō (era names) during the Edo period, where such designations were proposed by scholars and approved by the imperial court in consultation with the Tokugawa shogunate to invoke auspicious outcomes after calamities.^[8] Unlike later practices under the one-reign-one-era system established in 1868, pre-Meiji era changes like this one were not strictly tied to imperial succession but often responded to disasters or political needs, aiming to ritually reset the calendar and symbolize renewal.^[8] The name's adoption underscored hopes for pacifying the era's mounting tensions, though it ironically preceded further upheavals, including the Ansei Great Earthquake later that year on December 23, 1854.

Duration and Calendar Equivalents

The Ansei era extended over six numbered years in the Japanese calendar system, from Ansei 1 to Ansei 6, with the era name terminating early in what would have been Ansei 7.^[9] In Gregorian terms, the period lasted approximately 5 years and 4 months, beginning in November 1854 and ending in March 1860.^[10] The start date corresponds to the 22nd day of the 11th month of Kaei 7 in the lunisolar Japanese reckoning, while the end aligns with the adoption of the subsequent Man'en era name amid routine administrative changes typical of nengō transitions.^[11] Calendar equivalents reflect the offset between the lunisolar Japanese system—where years began around late winter or early spring—and the Gregorian solar calendar, resulting in each Ansei year overlapping two Gregorian years. The era thus covered portions of Gregorian years 1854 through 1860.^[12]

Ansei Year	Gregorian Equivalents
1	1854 (late)–1855
2	1855–1856
3	1856–1857
4	1857–1858
5	1858–1859
6	1859–early 1860

Exact day-level conversions vary slightly across sources due to lunisolar intercalations, with some placing the Ansei inception on 27 November 1854 and others on 15 January 1855 Gregorian.^[13]

Natural Disasters

The Ansei Earthquake Series

The Ansei great earthquakes comprised a series of destructive seismic events that struck Japan between late 1854 and 1855, during the early phase of the Ansei era. These included the Ansei Tōkai earthquake on December 23, 1854, followed approximately 31 hours later by the Ansei Nankai earthquake on December 24, 1854, and the Ansei Edo earthquake on November 11, 1855.^[14]^[15] The 1854 events originated along the Nankai Trough subduction zone, with the Tōkai quake rupturing segments off central Honshu and the Nankai extending southwestward, while the 1855 Edo event occurred inland near the de facto capital of Edo (modern Tokyo), independent of the trough but amid broader regional activity.^[16]^[17] Collectively, these quakes highlighted Japan's vulnerability to plate boundary tectonics, with the subduction of the Philippine Sea Plate beneath the Eurasian Plate driving the 1854 pair.^[14] The Ansei Tōkai earthquake registered a moment magnitude of approximately 8.4, with its epicenter ranging from Suruga Bay to the Enshū Sea, causing widespread shaking across eastern Japan and generating a tsunami that inundated coastal areas up to 6 meters high in some locations.^[14]^[18] It struck around 9:00 a.m. local time, destroying thousands of structures in regions like Shizuoka Prefecture through ground motion, liquefaction, and fires, with coseismic uplift reaching 1.8 meters in parts of the Yaizu Plain.^[19]^[18] The ensuing Ansei Nankai earthquake, also magnitude 8.4, epicentered off the Kii Peninsula around 4:00 p.m. on December 24, propagated rupture along adjacent Nankai Trough segments and triggered tsunamis with run-up heights exceeding 5 meters in Wakayama and Kochi, compounding damage from the prior event.^[14]^[20] Together, the 1854 quakes resulted in about 3,000 fatalities, primarily from tsunami drowning and structural collapse, alongside the destruction of over 20,000 homes.^[21] The Ansei Edo earthquake, estimated at magnitude 7.0, occurred at approximately 10:00 p.m. on November 11, 1855, with its hypocenter beneath the Kanto Plain, producing intense shaking that reached XI on the Modified Mercalli intensity scale in central Edo.^[22]^[16] Unlike the 1854 events, it generated no significant tsunami but ignited massive fires in the densely packed wooden city, fueled by nighttime conditions and strong winds, which razed over 10,000 buildings and accounted for most of the 7,000 to 10,000 deaths.^[1]^[22] Ground failures, including fissures and sand blows, further exacerbated damage to infrastructure like bridges and canals, while foreshocks and aftershocks prolonged the crisis.^[16] These earthquakes, occurring amid political turmoil from foreign pressures, strained the Tokugawa shogunate's resources and foreshadowed broader societal shifts.^[1]

Immediate Impacts and Government Responses

The Ansei-Tōkai earthquake struck on December 23, 1854 (Gregorian calendar), with an estimated magnitude of 8.4, epicentered off the coast near present-day Shizuoka Prefecture, generating intense shaking that collapsed over 10,000 structures across the Tōkai region and triggered a tsunami with waves reaching heights of up to 6 meters in some coastal areas.^[21] The immediate effects included widespread inundation of low-lying settlements, landslides in mountainous terrain, and fires sparked by toppled lanterns and hearths, exacerbating structural failures in wooden buildings unresistant to seismic forces. Casualties numbered in the hundreds directly from the shaking, with additional deaths from the tsunami and subsequent chaos, contributing to the overall toll for the paired events.^[23] The following day, December 24, 1854, the Ansei-Nankai earthquake (magnitude 8.4) ruptured farther west along the Nankai Trough, affecting areas from Wakayama to Kyūshū, destroying more than 20,000 houses in total across both quakes, washing away 15,000 others via tsunami surges, and burning an additional 6,000 structures.^[23] Combined fatalities reached approximately 3,000, primarily from drowning in tsunamis that propagated southward, devastating fishing communities and ports like those in Shimoda, where over 800 houses were obliterated and 122 lives lost locally.^[24] Economic disruption was acute, with rice stores and infrastructure losses compounding famine risks in an already agrarian society strained by prior events like the 1853-1854 arrival of Commodore Perry's fleet.^[25] The Tokugawa shogunate, led by Shōgun Tokugawa Iesada, initiated relief operations by dispatching officials to assess damage and distribute emergency rice rations from national reserves to affected domains, while urging daimyō to provide local aid and temporary housing.^[1] In Shimoda, Russian Admiral Yevfimiy Putyatin—negotiating a treaty amid Japan's sakoku isolation—extended humanitarian assistance, including food and medical supplies to survivors, an unprecedented foreign intervention that highlighted the shogunate's limited capacity and inadvertently softened resistance to diplomatic overtures.^[24] These efforts, though logistically challenged by poor communications and aftershocks, prevented broader societal collapse but strained bakufu finances, foreshadowing fiscal pressures that influenced later policy shifts toward partial Western engagement.^[26]

Foreign Relations

Pressure from Western Powers

Following the initial coerced opening under the Treaty of Kanagawa, signed on March 31, 1854, between the United States and the Tokugawa shogunate, Western powers intensified diplomatic and naval pressures to expand commercial access and consular presence in Japan. Commodore Matthew C. Perry's second expedition, comprising seven warships including two steam frigates, had anchored in Edo Bay in February 1854, demonstrating superior naval technology that underscored Japan's vulnerability after over two centuries of sakoku isolation policy. The treaty provisioned limited port access at Shimoda and Hakodate for American vessels seeking supplies and shelter, while establishing provisions for a U.S. consul, though it deferred broader trade negotiations.^[27]^[28] Russia exerted parallel pressure through Admiral Yevfimy Vasilyevich Putiatin's squadron, which had arrived in late 1853 but persisted into the Ansei period despite setbacks like the wrecking of ships in the December 23, 1854, Ansei-Tōkai earthquake tsunami at Shimoda. Putiatin negotiated the Treaty of Shimoda on February 7, 1855, mirroring Kanagawa's limited openings but adding Sakhalin and Kuril Islands border delineations amid territorial ambitions fueled by Russia's Pacific expansion. The incident with the Russian frigate Diana, damaged in Shimoda Bay during the quake, highlighted ongoing foreign naval presence even amid natural calamities.^[29] By 1856, American consul Townsend Harris arrived in Shimoda, advocating for full commercial reciprocity despite shogunal resistance and epidemics that claimed Japanese officials' lives. Harris leveraged U.S. naval support, including visits by warships, to press demands; his persistence culminated in the Treaty of Amity and Commerce signed July 29, 1858, aboard the USS Powhatan, granting extraterritoriality, fixed low tariffs (e.g., 20% on imports), and access to ports like Kanagawa (near Yokohama) for trade and residence. This "Harris Treaty" included most-favored-nation clauses, compelling Japan to extend terms to other powers.^[30]^[31] Britain and France, emboldened by opium trade victories in China, dispatched squadrons in 1858 to enforce similar concessions, with British envoy James Bruce, 8th Earl of Elgin, and French representative Guillaume Alphonse Marie Hubert Vivien de Saint-Martin arriving amid threats of bombardment. These efforts yielded the Anglo-Japanese Treaty on October 14, 1858, and the French treaty on October 9, 1858, both incorporating Harris-like unequal provisions without Japanese tariff autonomy or judicial equality. Collectively termed the Ansei Treaties, these pacts—signed under duress from combined Western fleets totaling dozens of steam-powered vessels—exposed Japan's technological and military disparities, forcing port openings by 1860 and eroding shogunal sovereignty.^[32]

Negotiation and Signing of the Ansei Treaties

The negotiations for what became known as the Ansei Treaties were precipitated by sustained diplomatic pressure from Western powers seeking expanded commercial access following Commodore Matthew Perry's 1853-1854 expeditions, which had already compelled Japan to sign the limited Treaty of Kanagawa. Townsend Harris, appointed the first U.S. consul general to Japan, arrived at Shimoda in August 1856 and initiated talks for a broader Treaty of Amity and Commerce, demanding open ports, consular rights, and extraterritoriality amid Japanese reluctance to erode sakoku isolation policies. Over nearly two years, Harris's persistence—bolstered by demonstrations of U.S. naval power, including the East India Squadron's arrival in early 1858—shifted the shogunate's calculus, as officials weighed the risks of war against concession.^[30]^[31] In April 1858, Ii Naosuke of Hikone Domain assumed the position of Tairo (chief minister), consolidating shogunal authority and advocating treaty ratification to avert armed conflict and stabilize governance. Under his direction, the shogunate signed the U.S. treaty on July 29, 1858 (Ansei 5, 19th day of the 6th month), aboard the USS Powhatan in Edo Bay, without awaiting Emperor Kōmei's explicit approval—a move justified internally as necessary for national defense but later criticized as overreach. The agreement opened ports at Hakodate, Nagasaki, and Yokohama (later Kanagawa) to American ships and merchants, fixed import/export duties at 5% ad valorem, permitted U.S. consular residences, and extended most-favored-nation privileges, while granting extraterritorial jurisdiction to American courts for their nationals.^[33]^[34] To forestall similar demands from rival powers leveraging the U.S. precedent, Ii Naosuke's administration rapidly concluded parallel treaties: with the Netherlands on August 18, 1858; Russia on August 19, 1858; the United Kingdom on August 26, 1858; and France on October 9, 1858. These Ansei Treaties mirrored the U.S. terms, imposing fixed low tariffs, extraterritoriality, and unequal trade concessions that disadvantaged Japan economically and juridically, while opening five ports total (adding Niigata and Hyōgo/Kōbe later) and allowing foreign settlements. Ratifications proceeded swiftly, with the U.S. exchange occurring in Washington on May 22, 1859, activating the framework amid domestic debate over sovereignty erosion.^[35]^[34]

Domestic Politics

Rise of Ii Naosuke and Shogunal Authority

In the wake of Prime Minister Hotta Masayoshi's failed mission to Kyoto in 1857 to secure imperial ratification for the proposed Harris Treaty with the United States, the Tokugawa shogunate faced intensifying internal divisions and external pressures, creating an opportunity for decisive leadership.^[36] Ii Naosuke, daimyō of the fudai domain of Hikone since 1850, emerged as a key figure due to his clan's historical eligibility for the rare position of tairō (great elder or chief minister), a role that allowed one individual to dominate shogunal policy amid crisis.^[37] Despite lacking seniority among the rōjū (senior councilors), Ii's strategic alliances with pro-shogunal factions, including support for the young Tokugawa Yoshitomi as heir over the rival Hitotsubashi Yoshinobu in the shogunal succession dispute, positioned him to consolidate influence.^[38] On April 23, 1858, Shōgun Tokugawa Iesada appointed Ii as tairō, granting him extraordinary authority to negotiate treaties independently and override collective rōjū deliberations, thereby recentralizing power in the shogun's hands after years of diffused decision-making under Abe Masahiro and Hotta.^[39] This appointment, the first tairō since the early 19th century, reflected Ii's success in portraying himself as the resolute defender of shogunal sovereignty against both foreign demands and domestic sonnō jōi (revere the emperor, expel the barbarians) agitation, which threatened to elevate imperial influence over bakufu affairs.^[37] By July 29, 1858, Ii had signed the Treaty of Amity and Commerce with the U.S. without prior imperial approval, asserting shogunal prerogative in foreign policy and temporarily stabilizing the regime against immediate collapse.^[36] Ii's tenure marked a brief resurgence of shogunal authority through administrative reforms that curtailed daimyō autonomy and reinforced bakufu oversight of han (domain) finances and military obligations, countering the decentralizing trends exacerbated by the Ansei earthquakes and commodity shortages.^[39] He advocated for defensive modernization, including coastal fortifications and Western-style artillery, while suppressing public discourse on treaty opposition to prevent erosion of central control.^[38] This centralization, however, relied on Ii's personal dominance, as he marginalized dissenting rōjū and leveraged Hikone retainers in key posts, fostering a top-down governance model that prioritized shogunal survival over consensus.^[37]

The Ansei Purge: Suppression of Dissent

The Ansei Purge, also known as Ansei no taigoku, was a systematic campaign of political repression conducted by Tairo Ii Naosuke and his allies within the Tokugawa shogunate from late 1858 to 1860, aimed at eliminating opposition to Ii's unilateral signing of treaties with Western powers and consolidating bakufu authority.^[40]^[41] Following the ratification of the Harris Treaty on July 29, 1858, without prior imperial sanction—a move that defied traditional protocols requiring consultation with the imperial court and key daimyo—Ii targeted critics who advocated sonnō jōi (revere the emperor, expel the barbarians) or sought to curb shogunal autonomy.^[42] This included rivals within the bakufu, imperial court officials, and samurai from anti-foreign domains such as Mito and Chōshū, whose dissent threatened Ii's strategy of managed accommodation with foreign demands to avert military coercion.^[43] The purges commenced on July 5, 1858 (lunar calendar, equivalent to August 15 Gregorian), with the house arrest of Tokugawa Nariaki, the former daimyo of Mito and a vocal treaty opponent, alongside the confinement of Tokugawa Yoshikuni, daimyo of Owari.^[40] Over the ensuing months, Ii ordered the dismissal, exile, or imprisonment of more than 100 figures, encompassing 20 imperial court nobles and their retainers, 9 bakufu officials, and 20 samurai from various han, many of whom were stripped of positions or domains.^[42]^[40] A subsequent wave in August 1859 further demoted figures like Tokugawa Yoshinobu, daimyo of Hitotsubashi, who had competed for shogunal succession.^[40] While most victims faced administrative penalties rather than capital punishment, reflecting a calculated restraint to avoid alienating broader elites, at least 7 to 8 were executed by beheading, including the scholar-activist Yoshida Shōin of Chōshū on October 21, 1859, and military strategist Hashimoto Sanai of Fukui, both convicted of plotting against the bakufu.^[43]^[42] Additional deaths occurred in custody due to harsh conditions, amplifying perceptions of brutality. Though the purge temporarily neutralized organized resistance, enabling Ii to install loyalists and stabilize shogunal policy amid foreign pressures, it deepened underlying fissures by radicalizing surviving loyalists and fostering covert networks of resentment.^[43] Critics within domains like Satsuma and Tosa, spared direct purges but wary of bakufu overreach, began reevaluating alliances, while executed figures like Shōin became martyred symbols of imperial restorationism.^[42] The campaign's reliance on arbitrary enforcement—often bypassing due process in favor of swift interrogations by bakufu spies—underscored the shogunate's vulnerability to internal challenges, ultimately contributing to the erosion of its legitimacy in the lead-up to the Bakumatsu upheavals.^[40]

Effects of Disasters and Openings on Society

The Ansei earthquakes of 1854–1855, including the magnitude 8.4 Ansei Nankai and Tōkai quakes on December 23–24, 1854, and the magnitude 6.9–7.0 Ansei Edo quake on November 11, 1855, inflicted severe societal tolls, with the Edo event alone claiming an estimated 7,000–10,000 lives amid widespread fires and structural collapse in the shogun's capital.^[22]^[44] These disasters displaced tens of thousands, exacerbating urban poverty and prompting mass migrations from rural areas strained by crop failures and aftershocks, while reconstruction demands spurred a temporary economic boom that redistributed wealth from elites and daimyo to skilled laborers and builders.^[1] Culturally, the quakes were interpreted through folk beliefs as manifestations of the catfish deity Namazu's thrashing, symbolizing chaotic wealth equalization, which resonated amid existing class tensions but also fueled perceptions of divine disfavor toward the bakufu's rule during a year of heightened religious observance known as okagedōshi.^[44]^[45] The Ansei Treaties of 1858, which opened ports like Yokohama and Nagasaki to limited foreign trade under unequal terms including extraterritoriality and fixed low tariffs, introduced profound social frictions by exposing Japanese society to Western technologies, goods, and personnel, eroding traditional isolationist norms and igniting xenophobic backlash.^[34] This influx disrupted domestic artisan economies, as cheap imported textiles and metals undercut local producers, contributing to inflation, currency instability, and localized unemployment in craft sectors by the late 1850s.^[46]^[47] Socially, the treaties' perceived humiliation—conceding sovereignty without reciprocal rights—galvanized intellectual and samurai opposition, fostering movements like sōnō jōi (revere the emperor, expel the barbarians) that channeled elite discontent into calls for national unification and expulsion of "barbarians," while urban commoners grappled with novel encounters that blurred social hierarchies.^[48] Interacting with disaster-induced vulnerabilities, these openings amplified societal instability: post-quake fiscal strains on the bakufu limited effective responses to trade imbalances, heightening famine risks in affected regions and eroding public trust in centralized authority, as evidenced by increased urban unrest and prophetic millenarianism portraying calamities as portents of regime change.^[49] This convergence strained traditional Confucian social orders, prompting pragmatic adaptations such as embryonic fire brigades in Edo and selective adoption of Western surveying techniques for seismic mapping, yet ultimately deepened fissures that presaged broader political realignments.^[1]^[45]

Intellectual and Cultural Shifts

The Ansei earthquakes, especially the destructive Ansei Edo quake of November 11, 1855 (magnitude approximately 6.9–7.0), which killed an estimated 8,000–10,000 people primarily in urban Edo through fires and structural collapses, spurred a surge in namazu-e woodblock prints as a key cultural medium for processing trauma and voicing dissent.^[44] These prints revived folklore of the giant subterranean catfish namazu, pinned by the god Kashima's sacred stone (kaname-ishi), portraying seismic thrashing not merely as divine punishment but as yonaoshi—a corrective upheaval redistributing wealth from corrupt elites (like daimyo and merchants hoarding rice) to laborers and firefighters who rebuilt society.^[44] Produced in the hundreds in the quake's immediate aftermath, often under loose censorship, they blended humor, satire, and moral allegory, critiquing shogunal incompetence in disaster relief while evoking resilience through depictions of communal aid and economic revival via construction booms.^[50] This visual genre marked a populist turn in popular culture, embedding social commentary in everyday art forms like ukiyo-e and foreshadowing later seismic iconography in Japanese hazard awareness.^[44] Intellectually, the disasters intertwined with foreign pressures from Perry's 1853–1854 expeditions and the 1858 Ansei Treaties, eroding confidence in Tokugawa cosmology and governance by highlighting systemic vulnerabilities—such as unequal urban soil liquefaction that spared plebeian areas but devastated elite districts.^[51] This catalyzed reevaluations blending folk beliefs (e.g., yin-yang imbalances) with emerging scientific inquiries into seismicity, prompting early advocacy for empirical observation over purely metaphysical explanations and influencing nascent mitigation strategies.^[51] Concurrently, the treaties' unequal terms accelerated pragmatic engagement with Western knowledge, extending Rangaku's focus on Dutch-transmitted sciences to direct study of gunnery, navigation, and medicine; by 1859–1860, shogunal institutes like the Bansho Shirabesho employed translators to dissect European texts, prioritizing defensive technologies amid fears of colonization.^[52] These shifts reflected a tension between sonnō jōi (revere emperor, expel barbarians) rhetoric and utilitarian adaptation, with intellectuals like those in the purge-suppressed but persistent reform circles weighing national sovereignty against empirical necessity.^[53] Religiously, the quakes triggered an okagedōshi phenomenon of fervent pilgrimages and millenarian upsurges, reinforcing shinkoku notions of Japan as a divine land while exposing fractures in official Shinto-Buddhist orthodoxy; mass processions to shrines like Kashima surged, interpreting tremors as calls for moral renewal amid political stasis.^[45] Overall, these developments underscored a broader pivot from insular stasis toward causal realism in interpreting crises—disasters as products of both natural forces and human mismanagement—laying groundwork for the intellectual ferment preceding the Meiji Restoration.^[51]

Conclusion of the Era

Assassination of Ii Naosuke

The assassination of Ii Naosuke, known as the Sakuradamon Incident, took place on March 24, 1860 (March 3 in the lunar calendar), outside the Sakurada Gate of Edo Castle in central Edo (modern Tokyo).^[54]^[55] Ii, serving as tairō (chief elder) of the Tokugawa shogunate since 1858, was en route in a palanquin procession to an audience with Shogun Tokugawa Iesada when approximately 18 rōnin samurai launched a coordinated sword attack.^[55] The assailants, primarily from Mito Domain with at least one from Satsuma Domain, targeted Ii due to widespread resentment over his unilateral negotiation and signing of the Ansei Treaties with Western powers without imperial approval, as well as his role in the Ansei Purge that suppressed sonnō jōi (revere the emperor, expel the barbarians) advocates.^[54]^[55] The attackers overwhelmed Ii's guards amid a snowy morning, slashing through the palanquin and inflicting multiple wounds before Satsuma rōnin Arimura Jizaemon beheaded him.^[54]^[55] Of Ii's retainers, four were killed immediately and 19 wounded, with four more dying later from injuries.^[55] Among the assassins, two were killed on the spot, three mortally wounded, and one committed seppuku nearby at Tatsunokuchi; eight surrendered to authorities from allied domains, while others fled to Kyoto.^[55] Arimura Yusuke, brother of the decapitating assassin, was detained and ordered to commit seppuku by Satsuma Domain authorities.^[54] In the immediate aftermath, the shogunate suppressed news of the killing for months, reflecting shock at the breach of security and the symbolic blow to its authority.^[56] Captured perpetrators faced execution in August 1861 after investigations, during which Satsuma Domain allegedly bribed shogunal messengers with goods like sea bream and possibly cash equivalents to obstruct inquiries, as revealed in newly analyzed correspondence.^[55]^[54] The incident underscored the fragility of shogunal control amid mounting domestic opposition to foreign engagement, accelerating political instability and contributing to the effective end of the Ansei era.^[54]

Transition to the Man'en Era and Immediate Aftermath

The Ansei era concluded on March 18, 1860, with the imperial court proclaiming the Man'en era the following day, signaling a hoped-for period of prolonged peace and prosperity amid ongoing political tensions.^[8] This transition occurred under Emperor Kōmei, as era names were selected to invoke auspicious connotations following the natural disasters and foreign pressures that characterized Ansei.^[8] Just five days into the new era, on March 24, 1860, Ii Naosuke, the tairo (chief minister) who had dominated shogunal policy through the Ansei Purge and treaty signings, was assassinated at the Sakurada Gate of Edo Castle by seventeen rōnin primarily from Mito and Satsuma domains.^[57] The attackers, motivated by opposition to the unequal treaties with Western powers and Ii's suppression of dissent, struck as Ii traveled in a procession, killing him and several guards in a bold daylight assault.^[58] In the immediate aftermath, the shogunate concealed Ii's death for nearly a month to avoid signaling weakness, but the incident eroded its authority and intensified domestic unrest.^[36] Officials responded by enhancing security measures around Edo Castle and daimyo residences, including restricting public access and bolstering guards, yet this failed to quell rising anti-foreign sentiment and attacks on Westerners.^[59] Politically, Ii's hardline centralization gave way to a more conciliatory stance; Andō Nobumasa briefly assumed acting tairo duties, but the regime began releasing Ansei Purge prisoners and consulting the imperial court more deferentially, marking a shift toward accommodation with oppositional factions like sonnō jōi advocates.^[60] This weakening of shogunal control foreshadowed further instability in the Bakumatsu period.^[36]

Legacy

Role in Bakumatsu Instability

The Ansei Purge of 1858–1859, orchestrated by Tairō Ii Naosuke to consolidate shogunal authority amid debates over foreign treaties, resulted in the execution or imprisonment of over 100 officials, scholars, and samurai opposed to opening Japan.^[42] This repression targeted advocates of sonnō jōi (revere the emperor, expel the barbarians), including the execution of Chōshū domain intellectual Yoshida Shōin on November 21, 1859, whose private academy had trained future imperial loyalist leaders such as Takasugi Shinsaku and Itō Hirobumi.^[61] While temporarily silencing dissent, the purge fostered deep resentment among lower-ranking samurai and han (domain) elites, who viewed it as an overreach that undermined traditional Tokugawa legitimacy.^[37] The accumulation of grievances erupted in the Sakuradamon Incident on March 24, 1860 (February 3 by lunar calendar), when 17 rōnin primarily from Mito domain assassinated Ii Naosuke outside Edo Castle's Sakuradamon Gate.^[54] This high-profile killing, motivated by opposition to Ii's unilateral treaty signings and purges, symbolized the purge's failure to eradicate anti-foreign sentiment and instead radicalized it into direct action against shogunal figures.^[36] In the aftermath, the shogunate adopted a more conciliatory stance toward the imperial court and han opposition, but this concession exposed its vulnerabilities, encouraging further terrorist acts by shishi (men of purpose) against pro-opening officials.^[36] These events intensified Bakumatsu-era instability by fracturing the shogunate's monopoly on coercion, empowering domain-based militias, and accelerating the shift toward court-centered politics. The purge's martyrs and the assassination's precedent validated political violence as a tool for reform, contributing to the alliance of Satsuma and Chōshū domains that ultimately toppled Tokugawa rule in 1868.^[36] Economic strains from Ansei-era disasters, including the 1854–1855 great earthquakes, compounded this turmoil by eroding fiscal stability and public confidence in the regime's competence.^[36]

Long-Term Assessments of Shogunal Policies

The shogunal policies enacted during the Ansei era (1854–1860), spearheaded by Tairo Ii Naosuke, sought to centralize authority and accommodate foreign demands amid mounting external pressures from Western powers. The signing of the United States-Japan Treaty of Amity and Commerce on July 29, 1858—without prior imperial approval—prioritized averting naval bombardment over traditional sakoku isolationism, granting extraterritorial rights and low import duties that flooded markets with cheap foreign goods, inflating prices for essentials like rice and silk while depleting silver reserves through export imbalances. These diplomatic concessions, extended to Britain, France, Russia, and the Netherlands by 1860, temporarily forestalled conflict but sowed economic discontent among merchants and peasants, as domestic industries faced ruinous competition and currency debasement ensued from forced openness.^[36] Internally, the Ansei Purge (1858–1859) dismantled opposition by dismissing, exiling, or executing over 100 figures, including daimyo, court officials, and ronin advocating sonnō jōi ("revere the emperor, expel the barbarians"), thereby enforcing policy uniformity and elevating bakufu control over han domains. This crackdown, which targeted reformers like those in Chōshū and Satsuma, yielded immediate quiescence, allowing Ii to orchestrate a brief resurgence in shogunal prestige through administrative reforms and military modernization experiments. Yet assessments highlight its pyrrhic nature: by alienating elite stakeholders and bypassing consultative mechanisms with the imperial court, the purge eroded the bakufu's Mandate of Heaven-like legitimacy, incubating latent resentments that manifested in escalated terrorism, including Ii's assassination at Sakurada Gate on March 24, 1860, by Mito domain ronin.^[36]^[62] Long-term evaluations underscore these policies' role in precipitating bakumatsu (end-of-shogunate) instability, as suppressed factions regrouped, forging alliances like the 1866 Satsuma-Chōshū pact that orchestrated the 1868 Restoration. While the era's pro-engagement stance inadvertently seeded infrastructural and technological adaptations—such as shipbuilding and gunnery imports that informed Meiji industrialization—the bakufu's top-down execution without domainal buy-in exposed systemic frailties, including fiscal insolvency from treaty indemnities and disaster relief (e.g., the 1858 Hietsu earthquake's aftermath). Historians argue this combination not only failed to resolve core vulnerabilities like samurai stipends amid commercialization but amplified perceptions of shogunal weakness, catalyzing a paradigm shift toward centralized imperial governance capable of unified response to global exigencies.^[36]^[62]

References

[1]
The Ansei Edo Earthquake and Catfish Prints | Gregory Smits
The Ansei Edo earthquake (Ansei Edo jishin 安政江戸地震) shook the de facto capital of Tokugawa Japan around 10:00 PM on November 11, 1855. However, the people ...
[2]
Seismic Japan: The Long History and Continuing Legacy ... - UH Press
In stockThe Ansei Edo earthquake shook the shogun's capital during a year of special religious significance and at a time of particularly vigorous seismic activity.Missing: era | Show results with:era
[3]
[PDF] The Merchants' Capital of Early Modern Japan - mimuw
Within Japan, the Ansei Purge of 1858-60 saw the shogunate defend its hegemony by summarily executing young samurai activists seeking political change. When ...
[4]
The Ansei Purge and the Tragedy of Yoshida Shoin - LinkedIn
Nov 21, 2024 · The Ansei Purge spanned from 1858 to 1859, cutting a bloody swath through Japan's political landscape. Naosuke initiated the purge by silencing ...Missing: era | Show results with:era
[5]
Ansei Facts for Kids
Oct 17, 2025 · It came after the Kaei era and before the Man'en era. This period lasted from November 1854 to March 1860.
[6]
Japanese Era Names - Jlit
The following table is meant as a quick guideline to Japanese era names since 645 CE. Dates are provided down to the month (lunar months up to the end of ...
[7]
Gonaitei - Kyoto Imperial Palace - 京都御所
The present Kyoto Imperial Palace was reconstructed in 1855 (Ansei 2), following the destruction of the previous palace complex by fire in 1854 (Kaei 7).
[8]
The Historical Background of How Japan Chooses Its Era Names
May 19, 2017 · In premodern Japan a new era name was sometimes adopted to mark the accession of a new emperor, but it was also common to change the gengō on ...
[9]
The Era name or Nengō (年号) naming system
The Era name or Nengō (年号) naming system ; 安政, Ansei, 1854-1860 ; 万延, Manei, 1860-1861 ; 文久, Bunkyu, 1861-1864 ; 元治, Genji, 1864-1865.
[10]
Ansei Period - InsideInside.org
Ansei Period. The Ansei period (1854–1860): The Ansei period was a short era during Japan's late Edo period. It is named after the Ansei era and was marked ...
[11]
Timeline of Political Events in Late Qing and Early Republican China
Timeline of the various political events in China between 1850 and 1937.
[12]
Japanese date conversion - Shinsengumi Archives - Tumblr
Jun 4, 2021 · For example, Ansei has offset 1853, so that year 1 of Ansei mostly coincides with 1854. However, the Ansei era started near the end of that ...<|separator|>
[13]
Japanese date conversion - CWI
The Ansei era (安政) started 1855-01-15, that is Ansei 1-11-27. The Japanese Wikipedia agrees, but the English one today calls this date November 27, 1854.
[14]
Time difference between the 1854 CE Ansei–Tokai and Ansei ...
Jan 5, 2022 · The time difference between the 1854 Ansei-Tokai and Ansei-Nankai earthquakes is estimated to be approximately 30.9 hours.
[15]
Kabuki Actor's Forgotten Manuscript Yields Clues About 1855 ...
Sep 8, 2020 · There were three great Ansei earthquakes: the Tokai and Nankai quakes, both in 1854 and both magnitude 8.4, and the Edo quake the following year ...
[16]
Magnitude and location of historical earthquakes in Japan and ...
Feb 24, 2005 · Historical data suggest, however, that the 1855 Ansei Edo earthquake was preceded by alterations in groundwater and springs and by “ground ...
[17]
Magnitude and location of historical earthquakes in Japan ... - USGS
If the 1855 earthquake was a Philippine Sea-Eurasian interplate event, the intensity center was adjacent to and downdip of the rupture area of the great 1923 ...
[18]
Tsunamis and submarine landslides in Suruga Bay, central Japan ...
Oct 1, 2020 · Coseismic uplift caused by the AD 1854 Ansei-Tokai earthquake is estimated to have been 1.8 m in the Yaizu Plain (Ishibashi, 1984). 3. Methods.
[19]
Seismic Intensity of the 1854 Ansei Tokai Earthquake in ... - J-Stage
The Ansei-Tokai Earthquake occurred at around 10:00 A.M. on December 23, 1854. The seismic intensity of the earthquake tended to be greater where Shizuoka and ...
[20]
Megaquake in the Making? The Expected Nankai Trough Earthquake
Aug 16, 2024 · Ansei Tōkai Earthquake (Dec. 23, 1854; M8.4) and Ansei Nankai Earthquake (Dec. 24, 1854; M8.4). Epicenters: Just 30 hours apart, the first quake ...
[21]
NCEI Hazard Earthquake Information - NOAA
300 people died in the earthquake and about the same number died in the tsunami. Total fatalities for the Dec 23 and 24, 1854 events: 3,000 and total houses ...
[22]
Researcher examines the history and impacts of earthquakes in Japan
Mar 19, 2014 · The Ansei Edo earthquake, estimated at 7.0 magnitude, shook the capital of Edo (now Tokyo) at about 10 p.m. on November 11, 1855, killing at ...
[23]
NCEI Hazard Tsunami Event Information - NOAA
Ansei Nankai Tsunami, Dec 24, 1854 with m=4, death toll was about 3,000 in Japan. Ref #11412: This is the true story of "the fire of rice sheaves," told in ...
[24]
[PDF] A HUGE SAND DOME FORMED BY THE 1854 EARTHQUAKE ...
The 1854 Ansei-Tokai earthquake brought massive destruction to Suruga Bay, central Japan. The earthquake triggered a large-scale tsunami, which surged over ...
[25]
HISTORY OF LARGE TSUNAMIS IN JAPAN | Facts and Details
A further 6,000 homes were damaged by fire. The tsunami washed away a further 15,000 houses and a total of 3,000 people died from either the earthquake or the ...Missing: immediate impacts
[26]
Seismic Shocks (Chapter 3) - Tokyo
Feb 6, 2025 · The shogunate's own finances were also strained by the earthquake as it hemorrhaged funds to pay for relief efforts, including the extension of ...
[27]
The Treaty of Kanagawa | National Archives
Mar 7, 2017 · The Fillmore administration sent Commodore Matthew C. Perry and a small fleet of sloops and the latest steam-powered ships to go to Edo (Tokyo) ...
[28]
Commodore Matthew C. Perry and the Opening of Japan
Aug 13, 2021 · Perry returned with a larger force in 1854, arriving in Edo (Tokyo) Bay, and obtained the signature of Japanese authorities to the Treaty of ...
[29]
Yevfimy Vasilyevich Putyatin - SamuraiWiki - Samurai Archives
Feb 6, 2020 · Yevfimy Vasilyevich Putyatin was a Russian naval captain who led a significant Russian mission to Japan and Ryûkyû in 1853-1854, ...
[30]
The United States and the Opening to Japan, 1853
The United States and Japan signed their first true commercial treaty, sometimes called the Harris Treaty, in 1858. The European powers soon followed the U.S. ...
[31]
Discussion of Harris Treaty - MIT Visualizing Cultures
The Harris Treaty—formally titled The United States-Japan Treaty of Amity and Commerce—was signed aboard the U.S. warship Powhatan (Perry's flagship in 1854) in ...
[32]
Japan's Ports and Power - Reconnecting Asia - CSIS
Jun 28, 2017 · Japan signed “unequal” commercial treaties, also known as the Ansei Treaties, in 1858 with the United States, the United Kingdom, Russia ...Missing: pressure | Show results with:pressure
[33]
Treaty of Amity and Commerce between the United States of ...
Munitions of war shall only be sold to the Japanese government and foreigners. No rice or wheat shall be exported from Japan as cargo, but all Americans ...Missing: 1856-1858 | Show results with:1856-1858
[34]
https://oxfordre.com/asianhistory/display/10.1093/acrefore/9780190277727.001.0001/acrefore-9780190277727-e-565
[35]
Japanese treaties of amity and commerce with the United States, the ...
In the same year, Japan signed similar treaties with the Netherlands (August 18, 1858), Russia (August 19, 1858), the United Kingdom (August 26, 1858), and ...
[36]
The Meiji Restoration: The End of the Shogunate and the Building of ...
Nov 29, 2018 · The year 1868 was crucial to the fall of the shogunate and the establishment of a new government, understanding the historical context requires a wider focus.<|separator|>
[37]
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[38]
Baron Ii Naosuke and the End of the Edo Period - TOTA
This tendency culminated at the time of the thirteenth of the line, Iyesada, (1833-1858) generally called Onkio-in. ... Tairo was the name of that highest office.
[39]
Bio - Ii Naosuke | Japan Reference
Oct 12, 2012 · While Ii took all administrative steps necessary to implement the commercial treaties with foreign nations, establishing new trade and port ...
[40]
Ansei Purge - SamuraiWiki - Samurai Archives
Aug 15, 2020 · The purges began as early as 1858/7/5, with Tokugawa Nariaki (former lord of Mito han) being sentenced to house arrest, and Tokugawa Yoshikumi ( ...Missing: historical details victims
[41]
Ansei Purge (nonfiction) - Gnomon Chronicles
Oct 17, 2023 · The Ansei Purge (安政の大獄 Ansei no taigoku) was a multi-year event in Japanese history of the Edo period between 1858 and 1860, ...
[42]
The Opening of the Country | The Pursuit of Power in Modern Japan ...
The Ansei Purge (1858–1899) and its Aftermath. The unequal treaties at once ... Visits made by French and British ships to Ryukyu in 1844–6 had alarmed ...Missing: 1850s | Show results with:1850s<|control11|><|separator|>
[43]
[PDF] li Naosuke's Attempt to Save the Tokugawa Shogunate
By the time Ii Naosuke became lord of the Hikone fief in. 1850 and thus acquired national prominence, the central bu- reaucracy of the Tokugawa government had ...
[44]
The Ansei Edo Earthquake and Catfish Prints
The Ansei Edo earthquake (magnitude 6.9-7.0) occurred in 1855, causing 8,000-10,000 deaths. Catfish prints often depicted the event, linked to a folk belief ...
[45]
The Long History and Continuing Legacy of the Ansei Edo ...
Smits argues the Ansei earthquake reshaped Edo society, influencing the daimyos' connection to the shogunate. 1855 marked an okagedoshi, leading to increased ...<|separator|>
[46]
Apocalypse Now: An Alternate View of the Bakumatsu Years
Again, no cure! A major fire that engulfed the center of Kyoto, barely sparing the imperial palace featured as the event for the year 1864. (Figure 9) The ...
[47]
[PDF] the economic and cultural effects of nineteenth century treaties in
Ansei Treaties (1858). In 1858, Japan signed a series of treaties known as the Ansei treaties with four other Western nations, which were the Netherlands ...
[48]
Vanguards of Civilization: Police Education and Unequal Treaty ...
Nov 10, 2019 · That year, Japan signed treaties with the United States, Great Britain, France ... Ansei Treaties a 'disgrace to Japan as a nation' in 1869.
[49]
The Long History and Continuing Legacy of the Ansei Edo Earthquake
One of the many accounts of the Ansei Edo earthquake was Record of the Great Earthquake and Great Storm (Ōjishin ōkaze kenmonki). Its title refers to the ...
[50]
Tales of the Catfish God: Earthquakes in Japanese Woodblock ...
Feb 21, 2024 · Legend has it that when the tremors of the 1855 Ansei Edo earthquake had finally subsided, there were so many dead that survivors were forced ...Missing: details | Show results with:details
[51]
The Long History and Continuing Legacy of the Ansei Edo ...
Aug 9, 2025 · What distinguished the Ansei Edo Earthquake from its many predecessors in Japan were the accidental circumstances of time (a spiritually charged ...<|separator|>
[52]
11 - The Problem of Western Knowledge in Late Tokugawa Japan
This chapter argues that “Western knowledge” was in fact the product of networks of mediation across South, Southeast, and East Asia.
[53]
4 1 8 Journal of Japanese Studies 37:2 (20 1 1 ) - jstor
This study of the relation between the national and the modern in "Ansei- treaty era Japan" is a bracing revision of late nineteenth-century intellectual.
[54]
New Light Shed on 1860 Assassination of Top Shogun Aide Ii ...
Mar 9, 2023 · It is believed that Ii was targeted because he signed a treaty with the United States without Imperial permission and persecuted pro-Emperor, ...
[55]
The Assassination of Baron Ii Naosuke - TOTA
The wound he had inflicted had its effect, for it disabled the man from going any farther than Tatsunokuchi, where he hastened death by his own ...
[56]
The Sakuradamon Incident - Samurai History & Culture Japan
Mar 24, 2025 · In April 1858, Ii Naosuke, lord of Hikone Domain, was appointed as Tairo, chief advisor to the shogun, and faced two major challenges: the ...
[57]
[PDF] Ii Naosuke
【Ii Naosuke】 Ii Naosuke (1815–1860) is remembered for his efforts to promote traditional arts and crafts, his involvement in opening up trade with the West, ...
[58]
Part 1. Major Incidents in Edo - Tokyo Metropolitan Library
March 1860 was the date of the Sakuradamon Incident, in which a chief minister of the Tokugawa Shogunate, Ii Naosuke, was assassinated by ronin samurais of the ...
[59]
Incident at Sakuradamon - SamuraiWiki - Samurai Archives
Aug 29, 2020 · The plot was organized and executed chiefly by rônin from Mito han, possibly at the direction of the lord of Mito, Tokugawa Nariaki, whose ...
[60]
THE LAST FIFTEEN YEARS OF THE TOKUGAWA SHŌGUNATE - jstor
During the Ansei period (1854 - 1859), models of small steamships and trains were made, and in the first year of. Bunkyu (1861), a factory for manufacturing ...
[61]
Yoshida Shōin: The Revolutionary and Teacher Who Helped Bring ...
Feb 4, 2015 · Yoshida Shōin (1830–59) was packed with incident, from an attempt to win passage to the United States on the ship of Commodore Matthew Perry to his execution.
[62]
Ii Naosuke | Research Starters - EBSCO
Ii Naosuke was a significant figure in mid-19th century Japan, known primarily for his role as the daimyo of Hikone and as a pivotal political leader.