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M2 medium tank

The M2 medium tank was an early American developed by the in the late as a transitional bridging light and heavier armored vehicles, featuring a single rotating armed with a 37 mm gun and multiple fixed sponsons for support. Designed by the Rock Island Arsenal starting in 1937 as the T5 prototype (with phases I through III incorporating improvements like enhanced volute spring suspension and rubber-bushed tracks), it was standardized as the in June 1939 and entered limited production that year. The tank's development addressed the Army's need for a more capable medium vehicle following the obsolescence of World War I-era designs, evolving from the M2 light tank platform with a taller hull for better crew accommodation and firepower. Production totaled 112 units: 18 initial M2 models in 1939 and 94 upgraded M2A1 variants in 1940–1941, all manufactured at Rock Island Arsenal, though plans for 1,000 units were scaled back due to rapid advancements in tank design. The M2A1 incorporated refinements such as a more powerful 400 hp Wright R-975 radial air-cooled engine (up from 350 hp in the M2), increased armor thickness up to 32 mm on the hull and turret, and a weight of approximately 23.5 short tons, enabling a top road speed of 30 mph (48 km/h) with a range of about 130 miles (210 km). Armament consisted of a 37 mm M5 gun in the turret (carrying 200 rounds) as the primary weapon, supplemented by six to eight .30 caliber M1919 Browning machine guns—four in fixed hull sponsons, one coaxial, and one on the turret roof—totaling up to 12,250 rounds of ammunition, reflecting an emphasis on anti-infantry roles over anti-tank capability. Although underpowered and thinly armored by World War II standards, the M2 series entered service in spring 1940 and proved valuable as a training platform for U.S. armored crews, replacing outdated Liberty and Mark VIII tanks at facilities like Fort Knox. It saw no combat deployments due to its obsolescence following the introduction of the M3 medium tank in 1941, but its mechanical and layout innovations—such as the volute suspension system and sponson design—influenced subsequent U.S. mediums like the M3 Lee/Grant and M4 Sherman. Variants included the T5E1 testbed for a Guiberson diesel engine in 1939, though none progressed beyond prototypes. By 1945, all M2s were retired from active use, with only three surviving today in museums.

Development

Origins and requirements

During the , the Army's tank doctrine was heavily shaped by experiences, where tanks were primarily viewed as tools for supporting advances by neutralizing enemy strongpoints, wire entanglements, and machine-gun nests. This perspective, codified in the 1920 National Defense Act, assigned tanks to the branch as a subordinate arm, emphasizing close coordination with foot soldiers rather than independent operations. Designs reflected this role through "hedgehog" configurations—multi-turreted vehicles bristling with machine guns to provide against —prioritizing volume of fire over anti-tank capabilities to aid breakthroughs in remnants. Observations of European tank developments in the early 1930s further influenced U.S. thinking, particularly reports from the (1936–1939) that showcased German and Soviet tanks with thicker armor and more potent guns, exposing vulnerabilities in lighter American designs to emerging anti-tank weapons like the 37 mm Pak 36. These insights, combined with the limitations of existing light tanks such as the and , prompted a doctrinal shift toward medium tanks capable of balancing support with greater protection and firepower, though persistent budget constraints—limited to around $60,000 annually for tank development from 1925 to 1931—hindered rapid progress. The push for a dedicated medium tank gained momentum through key figures like Brigadier General John K. Herr, Chief of Cavalry from 1938, and the Infantry Tank Board, established in 1924 to oversee experimental models and refine support tactics. Herr advocated for enhanced mechanized capabilities within cavalry units, while the Board tested modifications emphasizing offensive roles for tanks despite inter-branch rivalries. This culminated in the launch of the T5 program on May 21, 1936, approved by the Ordnance Committee as a successor to the , with initial specifications calling for a 10-12 ton vehicle mounting a 37 mm gun in a rotating and at least six .30 caliber machine guns for suppression. These requirements aimed to create a versatile platform for doctrinal needs, setting the stage for prototyping efforts that would refine the design into the standardized M2.

Prototyping and standardization

The development of the T5 medium tank prototypes began in 1936 as an enlargement of the design, with Phase I focusing on a basic 15-ton utilizing the same Wright R-975 radial engine, transmission, and (VVSS) system. Completed in 1937, this prototype featured a wooden mock-up and with a dummy 37 mm gun for initial evaluation, emphasizing foundational mobility and structural integrity without full armament integration. Phase II was proposed as a design study incorporating an alternative engine but was never constructed, allowing resources to shift toward more viable configurations. Phase III, introduced in late 1937, added a cast for the 37 mm M5 gun and sponson-mounted .30 caliber machine guns, increasing the weight to approximately 20 tons with enhanced armor up to 36 mm on the , while relocating to the left side for better . Testing of the prototypes occurred primarily at from November 1937 through 1938, evaluating performance across phases. Phase I trials, conducted from November 16 to December 29, 1937, with the wooden , and followed by metal tests in February 1938, demonstrated adequate at speeds up to 31 mph but highlighted vulnerabilities in armor thickness against contemporary anti-tank threats like the 37 Pak 36. Phase III evaluations in November–December 1938 revealed persistent issues, including poor due to the overweight design (exceeding 21 tons), unreliable steering mechanisms, and suboptimal placement that limited traverse and firing angles for both the main and secondary machine guns. These results prompted iterative modifications, such as refining the design for improved rotation and upgrading the to a 346 variant for better . Following successful adjustments, the Phase I design was standardized as the on June 1939 by the Ordnance Committee, incorporating the 37 mm gun and retaining the core chassis while addressing key turret and engine shortcomings identified in trials. Early production commenced at with 18 pilot vehicles completed in 1939 to validate manufacturing processes and conduct further field evaluations. However, observations from the 1939–1940 European conflicts, particularly the demonstrated inadequacy of single-gun medium tanks against emerging multi-turret or heavily armored designs, led to a rapid shift; production transitioned to the improved M2A1 variant starting in 1940, featuring a supercharged 400 hp engine, thicker side armor up to 32 mm, and redesigned turret with pistol ports for enhanced crew .

Design

Chassis, powertrain, and mobility

The chassis of the M2 medium tank was an enlarged adaptation of the M2 's design, featuring a multi-faceted hull structure with sloped plates and integrated sponsons for mounts. The suspension system employed the (VVSS), which consisted of three bogies per side, each supporting two road wheels, for a total of six road wheels per side; this setup provided improved stability over rough terrain compared to earlier configurations. The tracks measured 13.25 inches (33.66 cm) wide on the M2 and were widened to 14.25 inches (36.2 cm) on the M2A1 variant to better distribute weight. The powertrain centered on the , a nine-cylinder air-cooled radial , which delivered 350 horsepower in the base M2 model and was supercharged to 400 horsepower in the M2A1 for enhanced performance. This drove a with five forward speeds and one reverse gear, utilizing controlled operated by levers for maneuverability. The overall layout positioned the at the rear, with drive components routed along the floor, influencing the placement of the driver and assistant driver in the forward compartment. Mobility characteristics reflected the tank's interim design, with a combat weight of approximately 19 short tons (17.25 metric tons) for the M2 increasing to 23.5 short tons (21.3 metric tons) for the M2A1 due to added features. The top road speed reached 26 mph (42 km/h), while the operational was about 130 miles (210 km) on internal fuel tanks holding 125 U.S. gallons (473 liters). Ground pressure was approximately 15-19 (1.05-1.33 kg/cm²), enabling reasonable cross-country performance despite the narrow tracks, and the vehicle could water up to 2 feet (0.61 m) deep without preparation. The five-man crew—commander, gunner, loader/radio operator, driver, and assistant driver/bow gunner—occupied positions integrated into the , with the loader and assistant driver also manning the machine guns.

Armament and crew accommodations

The primary armament of the M2 medium tank consisted of a 37 mm M5 gun mounted in a 360-degree traversable , capable of elevating from -10 to +20 degrees and supplied with 200 rounds of ammunition, primarily armor-piercing projectiles for anti-tank engagements. This weapon, derived from designs, provided the tank's main offensive capability against armored targets, though its velocity and penetration were limited compared to later wartime standards. Complementing the main gun, the M2 carried six .30 caliber M1919A4 Browning machine guns as secondary armament, with a total ammunition stowage of 12,250 rounds distributed across the vehicle. These included one coaxial machine gun in the turret for synchronized fire with the 37 mm gun, two fixed forward-firing guns in the bow for the driver and assistant, two traversable guns in side sponsons (each with a 30-degree arc for close-range defense), and one on the turret roof for anti-aircraft protection. The arrangement embodied a "hedgehog" concept, enabling all-around small-arms fire to support accompanying infantry, though the sponson guns' restricted traverse angles hampered their effectiveness in dynamic combat scenarios. The M2 accommodated a five-man to manage its complex armament and operations: the tank commander and in the , in the front hull, the assistant driver/bow , and the loader/ who also operated the machine guns. Internal layout prioritized weapon access, with ammunition storage integrated into the fighting compartment floors and walls for quick reloading, but gunners faced severely limited visibility through narrow vision slits, often requiring the commander to direct their fire. Firing mechanisms for the machine guns were manually operated, relying on the crew's coordination to maintain during advances.

Armor and protection

The M2 medium tank's armor consisted of riveted and partially welded face-hardened rolled homogeneous plates, providing basic protection against and shell fragments but limited resistance to anti-tank weapons. On the original M2, armor thickness varied from 6 mm on the floor to 25 mm on the front plate, which was sloped at 30 degrees to improve ballistic deflection, while the sides and rear measured 19 mm and the turret front 25 mm. The M2A1 variant upgraded this protection with thicker plates, increasing the front hull and turret to 32 mm, though the roof remained thin at 9.5 to 12.7 mm, exposing the vehicle to top-down attacks or . The rear armor, at only 13 mm in some areas, was particularly vulnerable to penetration by contemporary anti-tank guns, such as the German 37 mm Pak 36, rendering the design obsolete against 1939-era threats beyond close ranges. Base models lacked spaced armor or appliqué additions, relying solely on the integral plate layout for defense without further enhancements. For situational awareness, the commander benefited from a cupola with vision slits, but sponson gunners had no periscopes, increasing their exposure during operation.

Production and variants

Production history

The development of the M2 medium tank began with the construction of two T5 prototypes at Rock Island Arsenal between 1937 and 1938, serving as the foundational models for the series. These prototypes underwent testing to refine the design before standardization. Initial production shifted to 18 pilot M2 tanks in 1939, also manufactured exclusively at in , , as the U.S. Army's primary armored vehicle facility at the time. This limited run focused on validating the design for potential scaling. By 1940, an order for 54 additional M2s was placed but not fully executed due to evolving priorities. Production of the improved M2A1 variant commenced in December 1940 at the same arsenal, yielding 94 units by August 1941, with a planned for 126 vehicles ultimately curtailed. On August 15, 1940, Chrysler Corporation was awarded a to produce 1,000 M2A1 tanks at a fixed unit price of $33,500, but this was rapidly redirected to the M3 medium tank program amid assessments that the M2A1 was obsolete for combat requirements. remained the sole manufacturer, constrained by its limited capacity and the broader wartime emphasis on higher-priority designs. The full production ramp-up was delayed by the pivot to the M3, resulting in a total production of 112 M2-series vehicles by 1942 (18 M2 + 94 M2A1), in addition to the two T5 prototypes. Challenges included supply bottlenecks for the Wright R-975 radial engine and reallocations driven by escalating global conflicts, which further limited output.

Variants and modifications

The T5E1 was a modification of a production M2 medium tank , retrofitted in 1939 with the Guiberson T-1020 radial air-cooled , rated at approximately 250 horsepower, to evaluate its performance and reliability as a potential replacement for the standard Wright R-975 . This modification aimed to address concerns over and engine overheating in the original design, but testing revealed significant reliability issues with the diesel unit, leading to its rejection for further adoption. The T5E2 represented another prototype effort to enhance the M2's firepower, featuring a 75 mm M3 pack mounted in a right-side rather than the standard armament. Developed in 1938 and tested at from April 1939 to February 1940, this configuration enlarged the hull to accommodate the , which demonstrated strong effectiveness against armored targets and fortifications during trials. However, the weapon's limited traverse—restricted to about 30 degrees—proved inadequate for dynamic , resulting in the variant's cancellation and no production; its -mounted gun concept nonetheless informed the armament layout of the subsequent M3 . In 1941, the U.S. Army's Chemical Warfare Service conducted experiments with a adaptation on , designated as the E2 , to explore close-assault capabilities. The E2 mechanical replaced the 37 mm , with fuel tanks integrated into the and machine guns retained for secondary armament; this single test vehicle carried about 100 gallons of fuel, enabling short bursts up to 40 yards. Trials highlighted limitations in range and fuel endurance, preventing wider modification or production beyond this prototype. Later modifications to existing M2 vehicles focused on enhancing communications for training roles. Some M2A1 tanks received upgrades to improve command coordination in armored units.

Operational history

Training and evaluation

Following the completion of production in , the medium tank, particularly its M2A1 variant, was deployed exclusively within the for crew training in the newly formed armored divisions. These vehicles equipped medium tank battalions in the 1st, 2nd, and 3rd Armored Divisions from to 1943, serving as interim platforms to familiarize personnel with medium tank operations, tactics, and maintenance prior to the widespread adoption of the and . The 67th Infantry Regiment (Medium Tanks), later reorganized as the 69th Armored Regiment, received a significant allocation and conducted initial training at , , where a was activated in 1939, though it remained understrength until fuller deliveries arrived. A total of 94 M2A1 tanks were produced between December 1940 and August 1941 at , with all units distributed to training schools and armored units for instructional purposes, replacing obsolete World War I-era vehicles like the Mark VIII. These tanks supported the Armored Force School at , , starting in November 1940, where over 200 officers and 2,000 enlisted men received education in gunnery, driving, and tactics. Adaptations for diverse environments included desert simulation exercises at Fort Knox and participation in maneuvers at Camp Polk, , emphasizing mobility in varied terrains to prepare crews for potential overseas operations. The M2 also participated in large-scale 1941 maneuvers, such as the Louisiana and exercises, where it helped test armored tactics. Evaluation during the 1941 maneuvers, including the large-scale exercises involving the 1st Armored Division, revealed critical shortcomings that informed subsequent designs. Reports highlighted the obsolescence of the sponson-mounted machine guns, which were vulnerable to enemy fire and difficult to employ effectively in dynamic combat scenarios due to their fixed positions and limited traverse. Additionally, maintenance challenges arose with the R-975 , an aircraft-derived powerplant prone to overheating and complex servicing in field conditions, exacerbating downtime during extended operations. These assessments, drawn from Third Army observations, underscored the need for streamlined armament and more reliable mechanical systems in future mediums. By mid-1943, as production ramped up, all M2 medium s were phased out of active training roles and reassigned to reserve depots and secondary schools for basic instruction. This transition allowed the armored divisions to standardize on more capable platforms, with the M2's contributions limited to domestic familiarization and the validation of key components like its suspension and , which influenced later U.S. tank development.

Combat service

The M2 medium tank saw no combat service during , as its design was already obsolete by late 1941, with thin armor and a 37 mm main gun that could not compete with contemporary tanks. All 112 produced units (18 M2 and 94 M2A1) were retained in the United States for training tank crews and testing components that influenced later designs like the M3 and . No M2 medium tanks were deployed to the with the Provisional Tank Group in 1941–1942, which relied on light tanks for engagements against forces on ; the group had been scheduled to receive medium tanks but received only lights before the Japanese invasion. Losses across all M2 variants during the war were primarily from training accidents and mechanical failures. The M2 was not provided under Lend-Lease to allies like the United Kingdom, as British evaluators rejected it in favor of more capable American designs such as the M3 medium tank; no exports occurred.

Legacy

Influence on later designs

The M2 medium tank served as the direct predecessor to the M3 Lee/Grant medium tank, which entered production in 1941 and retained the M2's lower hull, Wright R-975 radial engine, vertical volute spring suspension (VVSS), and rubber-bushed tracks while incorporating a 75 mm gun in a hull sponson to address firepower deficiencies observed in early evaluations. This design evolution allowed for rapid adaptation without starting from scratch, as the M3's chassis was essentially an enlarged and modified version of the M2's, enabling the U.S. Army to produce over 6,000 M3 variants by 1943 despite the tank's unconventional armament layout. Lessons from the M2's multi-turret and sponson machine gun configuration, which complicated production and crew operations, were directly incorporated into the , leading to the elimination of sponson guns, a redesigned single-turret housing the 75 mm gun, and retention of the M2-derived VVSS suspension for improved mobility and reliability. The , standardized in , built upon the M3's (and thus M2's) powertrain and hull basics, resulting in a more versatile platform that became the backbone of U.S. armored forces, with over 46,000 units produced. The M2's development and limited field testing exposed critical shortcomings in U.S. tank doctrine, such as over-reliance on light tanks and inadequate anti-tank capabilities, prompting a shift toward versatile medium tanks capable of independent maneuver in 1940s tactics. This doctrinal evolution emphasized operations with greater firepower and mobility, influencing the Armored Force's transition from infantry support roles to offensive breakthroughs seen in and . Production experience with the at provided essential groundwork for scaling up M3 and M4 manufacturing, as the facility's expertise in assembling complex chassis and powertrains accelerated the wartime output that exceeded 88,000 U.S. tanks overall by 1945. This legacy enabled multiple contractors to produce variants efficiently, underscoring the M2's role in establishing a robust industrial base for American armored vehicle development.

Surviving examples

Few surviving examples of the M2 medium tank remain today, with only three well-documented vehicles preserved primarily in military collections. These rare artifacts provide insight into early American armored vehicle development during the and training roles. One M2 medium tank, fitted with an experimental M2A1 , is held at the U.S. Army Training Support Facility (formerly the Ordnance Museum) in Fort Lee, . This example, serial number 2, was originally produced in 1940 at and previously displayed at the before the collection's relocation. It features early design elements such as pistol ports and serves as a static display illustrating transitional testing. An M2A1 medium tank is preserved at the U.S. Army Armor & Cavalry Collection in Fort Moore (formerly Fort Benning), Georgia. This vehicle, transferred from the former Patton Museum of Cavalry and Armor in Fort Knox, Kentucky, following the 2010 relocation of the Army's Armor School, is stored out of public view but has been the subject of maintenance and discussion by the National Armor and Cavalry Collection's restoration team. In a 2017 presentation, experts highlighted its historical value for understanding crew accommodations and armament configurations in pre-Sherman medium tanks. The T5 Phase I prototype, featuring twin 37 mm turrets and serial number 86 (USA 30369), is also preserved at the U.S. Army Armor & Cavalry Collection in , , where it is stored out of public view. This early developmental vehicle represents the initial prototyping phase of the M2 series. These preserved M2 tanks are featured in specialized exhibits focused on the of U.S. armor, emphasizing their role in doctrinal shifts toward more mobile designs before widespread combat deployment. No operational engines are present in these examples, and restoration efforts have prioritized structural integrity over full functionality.

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