The 37 mm gun M3 is the first dedicated anti-tank gun fielded by United States forces in numbers. Introduced in 1940, it became the standard anti-tank gun of the U.S. infantry with its size enabling it to be pulled by a jeep. However, the continuing improvement of German tanks quickly rendered the 37 mm ineffective and, by 1943, it was being gradually replaced in the European and Mediterranean theaters by the more powerful British-developed 57 mm gun M1. In the Pacific, where the Japanese tank threat was less significant, the M3 remained in service until the end of the war, but some 57mm guns were issued.
Like many other light anti-tank guns, the M3 was widely used in the infantry support role and as an anti-personnel weapon, firing high-explosive and canister rounds.
The M5 and M6 tank mounted variants were used in several models of armored vehicles most notably in the Stuart light tank M3/M5, the Lee medium tank M3, and Greyhound light armored car M8. In addition, the M3 in its original version was mated to a number of other self-propelled carriages.
The inability of the 37 mm round to penetrate the frontal armor of mid-war tanks severely restricted the anti-armor capabilities of units armed with them.
Development history In the mid-1930s, the United States Army had yet to field a dedicated anti-tank artillery piece; anti-tank companies of infantry regiments were armed with machine guns. Although some consideration had been given to replacing the machine guns with a more powerful anti-tank gun, the situation began to change only after the outbreak of the Spanish Civil War. Combat experience from Spain suggested that a light anti-tank gun, such as the German 37 mm PaK 35/36, was capable of neutralizing the growing threat posed by tanks.Zaloga – US Anti-tank Artillery 1941–45, p. 3–7.
In January 1937, the Ordnance Committee recommended development of such a weapon; two PaK 36 guns were acquired for study.Hogg – Allied Artillery of World War Two, p 149. As the projected main user of the weapon, the Infantry Branch was chosen to oversee the work. They wanted a lightweight gun that could be moved around by the crew, so any ideas of using a larger caliber than that of the German gun were discarded. The 37 mm was a popular caliber of anti-tank guns in the 1930s; other anti-tank guns of the same caliber included Swedish Bofors gun, Czechoslovak vz. 34 and vz. 37, Japanese Type 94 and Type 1.
Development and testing continued until late 1938. Several variants of gun and carriage were proposed until on 15 December a combination of the T10 gun and T5 carriage was officially adopted as the 37 mm gun M3 and carriage M4. Although the weapon followed the concept of the PaK 36 and was often referred to as a copy of it,E.g. see Rottman – The US Marine Corps 1941–45, p 17: "M3A1 ... was copied from the standard German AT gun" or Sayen – US Army Infantry Divisions 1942–43, p 13: "M3 or M3A1 towed guns were unlicensed versions of the German Pak 35/36". the M3 differed significantly from the German design and used different ammunition.
The gun was manufactured by Watervliet Arsenal and the carriage by Rock Island Arsenal. The first production examples of the M3 were delivered in July 1940. It took until August 1941 for production to accelerate, and some infantry antitank units were forced to use wooden mock-ups of the new gun or their original weapons (37 mm gun M1916) during the Louisiana Maneuvers and Carolina Maneuvers, and did not get their first weapons until late 1941. Production continued until October 1943.
+ Production of М3, numbers of piecesZaloga – US Anti-tank Artillery 1941–45, page 21. Month 1940 1941 1942 1943 January 40 609 894 February 639 625 March 2 394 452 April 57 752 290 May 12 1,002 200 June 63 962 400 July 20 72 921 600 August 75 188 1,104 500 September 75 366 1,099 152 October 128 555 1,501 185 November 31 451 1,338 December 11 446 1,491 Total 340 2,252 11,812 4,298
Minor changes in the gun construction were introduced during production. The carriage received a modified shoulder guard and traverse controls (carriage M4A1, standardized on 29 January 1942). Although ordnance requested an upgrade of all M4 carriages to M4A1, this process was not completed. Another change was a threaded barrel end to accept a big five-port muzzle brake (gun M3A1, adopted on 5 March 1942). According to some sources, the latter was intended to avoid kicking too much dust in front of the gun, which hindered aiming; however, the brake turned out to be a safety problem when firing canister ammunition and consequently the M3A1 went into combat without the muzzle brake. Other sources state that the muzzle brake was intended to soften the recoil, and that it was dropped simply because additional recoil control measures were not really needed.Chamberlain, Gander – Anti-Tank Weapons, page 47.
In an attempt to increase the armor penetration of the M3, several squeeze bore adapters (including the British Littlejohn adaptor) were tested; none was adopted. Experiments with rocket launchers on the M4 carriage (e.g. rocket projector T3) did not produce anything practical either.
Description The barrel was of one-piece forged construction, with uniform rifling (12 grooves, right-hand twist, one turn in 25 calibers). The breech end of the barrel was screwed into a breech ring. The breech mechanism was of standard vertical sliding-block type, but unlike the overwhelming majority of the anti-tank guns of the era, it was not semi-automatic, meaning that a crew member had to manually open and close the breech at each shot. The barrel was fitted with a hydrospring recoil system.Technical Manual TM 9-2005 volume 3, Infantry and Cavalry Accompanying Weapons, pages 11-15.
The carriage was of split trail type, with pneumatic tires but without any spring suspension whatsoever. Mounted on the axle next to the wheels were the "wheel segments"; these were segment-shaped supports that could be lowered to provide more stability in the firing position or raised so that they would not impede movement of the gun.
The telescopic sight on the M6 and both elevation and traverse controls were located on the left side, so one gunner was able to aim the gun. The traverse gear had a release mechanism which allowed free movement of the barrel in case a quick traverse was needed.
Organization
US Army Under the April 1942 organization, each infantry battalion had an anti-tank platoon with four 37 mm guns (1/4 ton trucks, better known as jeeps, were authorized as prime movers) and each regiment an anti-tank company with twelve (towed by 3/4 ton trucks). Each of the four divisional artillery battalions possessed six anti-tank guns, the combat engineering battalion had nine pieces (towed by M2 halftracks); in addition, the division's headquarters company had four (towed by 3/4 ton trucks) and the divisional maintenance company two.Sayen – US Army Infantry Divisions 1942–43, pages 9, 15, 25, 28, 33, 36.
In 1941, provisional antitank battalions had been formed from divisional or brigade anti-tank weapons (producing companies armed with 37 mm guns and 75 mm guns), in December 1941, these battalions became permanent and were reorganized as independent tank destroyer battalions. The towed guns of many battalions were replaced with self-propelled ones as soon as the latter became available.Zaloga – US Anti-tank Artillery 1941–45, pages 9-12.
In 1942, the first airborne divisions were formed. According to their October 1942 organizational structure, an airborne division had 44 37 mm anti-tank guns: four in divisional artillery (AA/AT battery of parachute field artillery battalion), 24 in the AA/AT battalion, and eight in each of two glider infantry regiments; parachute infantry regiments did not have anti-tank guns. In practice, airborne divisions often had only one glider infantry regiment and therefore 36 guns.Rottman – US Airborne Units in the Mediterranean Theater 1942–44, pages 30-39; Zaloga – US Airborne Divisions in the ETO 1944–45, pages 16-25, 33, 41.
37 mm guns were also issued to the infantry regiments of the only mountain division formed in the U.S.: the 10th Mountain Division.Anderson – US Army in World War II; Cavalry and Infantry.
Finally, U.S. armored divisions under the March 1942 organization possessed 68 37 mm anti-tank guns. Of these, 37 belonged to the armored infantry regiment (four in each company and one in regiment HQ); 27 to the armored engineer battalion; three to the divisional train and one to division HQ.Zaloga – US Armored Units in the North African and Italian Campaigns 1942–45, pages 24-28.
US Marine Corps Under the D-series Tables of Organization (TO) from 1 July 1942, the role of AT weapons in Marine Corps service was officially entrusted to 20 mm automatic guns, which were in the regimental weapons company (three platoons) and the battalion weapons company (one platoon). In practice, units used the World War I-era 37 mm M1916 for training. They were equipped with the M3 (four in each platoon) before being sent to the frontline. Additionally, a divisional special weapons battalion was equipped with self-propelled 37 mm GMC M6.Rottman – US Marine Corps Pacific Theater of Operations 1941–43, pages 25-30.
Under the E-series TO from 15 April 1943, self-propelled guns in the divisional special weapons battalion were replaced with eighteen 37 mm towed guns in three batteries of six; an infantry regiment had a weapons company with 12, in three platoons of four. The battalion-level AT guns were removed. In total, a division possessed 54 pieces. The F-series TO from 5 May 1944 removed the special weapons battalion from the divisional organization, resulting in a total of 36 guns per division. The subsequent G-series TO reduced regimental weapons companies to two platoons, meaning 24 pieces per division. Although the G-series TO was only adopted on 4 September 1945, in practice in some divisions this change was introduced early in 1945.History of U.S. Marine Corps Operations in World War II, Vol II: Table of Organization E-100, p 571, 572; Vol III: Table of Organization F-100, p 618, 619; Rottman – The US Marine Corps 1941–45, pages 5-8; ww2gyrene: The Marine Division; ww2gyrene: M3A1 37mm Antitank Gun.
Other operators The only major lend lease recipient of the M3 was the Chinese National Revolutionary Army (1,669 pieces). The gun was also supplied to Bolivia (4), Canada (3), Chile (198), Colombia (4), Cuba (1), El Salvador (9), France (130), Paraguay (12), United Kingdom (78), Soviet Union (63), Nicaragua (9), and other countries.Zaloga – US Anti-tank Artillery 1941–45, page 44. Some nations still had it in service in the early 1970s.
Combat service As an infantry anti-tank gun