Bofors 37 mm

The Bofors 37 mm gun was an anti-tank gun designed by Swedish manufacturer Bofors in the early 1930s. Licensed copies were produced in a number of countries. The gun was used by some European armies during World War II, mainly at the early stage of the war.

Development history
The gun was initially designed by Swedish manufacturer Bofors, mainly for export purposes. The first prototype was built in 1932; the development process continued until 1934. The Netherlands were the first to purchase the gun (order for 12 pieces was placed in 1935) and were followed by many other countries. Licensed copies were produced Denmark, Finland, the Netherlands and Poland.

The barrel was of monobloc type, with semi-automatic vertical sliding breech block and small muzzle brake. It was mounted on a split trail carriage which had suspension and metal wheels with rubber tires. To give the crew some protection from firearms and shell fragments, the gun was equipped with a 5 mm thick shield, with a folding lower plate.

Employment history
The Bofors gun saw combat for the first time in Spanish Civil War, where it could easily pierce the armor of contemporary light tanks.

The Polish guns were actively used during the German and Soviet invasion of Poland in 1939. Wołyńska Cavalry Brigade equipped with the Bofors 37 mm antitank gun beat the German Panzer Divisions in one of the first battles of the invasion; the Battle of Mokra. At that time, the armored forces of the Wehrmacht consisted mainly of light Panzer I and Panzer II tanks, which were vulnerable to the Bofors gun. Early models of the Panzer III and Panzer IV could also be penetrated at ranges up to 500 m. After Poland was occupied, most of the guns fell into the hands of the German and Soviet armies. The weapon was proven obsolete by 1941 during the Operation Barbarossa.

Even though only one Bofors AT-gun was in action in the Invasion of Denmark, it damaged two tanks, and shot the tracks of another tank, before its crew were either wounded or killed by a German tank destroyer which drove over the gun. The gun is now at the Tøjhusmuseet in Copenhagen.

During the Winter War, the Finnish guns were successfully used against Soviet tanks such as T-26, T-28 and BT. However in the Continuation War the gun was found to be ineffective against the T-34 and KV and was relegated to an infantry support role.

The gun was used to equip the British forces in North Africa, where it made up for the lack of the QF 2-pounder anti-tank guns after the Fall of France. It was often carried portee on the back of a vehicle.

Bofors guns were also employed in World War II by Germany, the Netherlands, Romania, Yugoslavia and USSR, but there are no detailed reports of their use.

Summary
When it was introduced, the Bofors 37 mm anti-tank gun was an effective weapon, able to deal with contemporary tanks. Its performance, light weight and high rate of fire made it a popular anti-tank weapon in the pre-war Europe. However, introduction of better armored tanks early in World War II made the gun obsolete (as it made obsolete other similarly performing weapons such as the German PaK 36 and the US 37mm M3.



Ammunition

 * Ammunition: AP with tracer, HE, WP incendiary
 * Projectile weight (AP): 0.70 kg
 * Penetration (AP shell, meet angle 60 degrees):
 * 300 yards: 40 mm
 * 457 yards: 33 mm
 * 600 yards: 30 mm
 * 900 yards: 20 mm
 * 1,200 yards: 15 mm

Operators

 * A version with slightly more powerful cartridge was manufactured by the Danish state arsenal Hærens Vaabenarsenal, as 37 mm Fodfolkskanon m1937. In 1945 Danish units returning to their homeland brought with them a few Swedish model 1938 guns.
 * 🇫🇮: As 37 PstK/36. 114 pieces were bought from Bofors in 1938-39 (some of them were returned to Sweden in 1940), 42 Polish-made guns were received from Germans in 1940-41 and 355 were produced by local manufacturers Tampella and VTT (Valtion Tykkitehdas - State Artillery Factory) in 1939-41. When the Winter War began in November 1939, the Finnish Army had 98 guns of the type. A tank version was also used to equip Finnish 6-tonne tanks. The gun remained in the Finnish Army inventory listings until 1986.
 * 🇩🇪 Germany: Used Polish guns captured in 1939 as 3,7 cm PaK 36(p) and Danish guns captured in 1940 as 3,7 cm PaK 157(d).
 * 🇳🇱: 12 pieces were ordered from Bofors in 1935. Later another 24 (or more) were procured. All these were used for Dutch (wheeled) AFV's, being 24 off Landsverk types L180 and L181 as well as 12 off DAF Pantrado cars.
 * 🇵🇱: As wz.36. 300 guns were bought in Sweden and hundreds more were produced by SMPzA (Stowarzyszenie Mechaników Polskich z Ameryki) in Pruszków, some of them exported. When World War II began, the Polish Army had 1,200 pieces. A tank variant, designated wz.37, was mounted in 7TP (single-turret version), 9TP (prototypes) and 10TP tanks. 111 of them were produced before the war.
 * 🇷🇴: 556 pieces (former Polish ones) were bought from Germany.
 * 🇪🇸: Some guns bought by the Republicans were used during the Spanish Civil War.
 * 🇸🇪: Adopted in 1937 as 37 mm infanterikanon m/34 (infantry gun model 1934). Modernized version was adopted in 1938 as 37 mm pansarvärnskanon m/38 (anti-tank gun model 1938) and 37 mm pansarvärnskanon m/38 F. The latter was also produced in a tank gun variant - 37 mm Kanon m/38 stridsvagn; it was fitted to Landsverk Strv m/38, Strv m/39, Strv m/40 light tanks and to the Strv m/41, a Swedish version of the Czech TNH light tank.
 * A number of Swedish m/34 ordered by Anglo-Egyptian Sudan were adopted as Ordnance QF 37 mm Mk I.
 * Several dozens of Polish guns fell into Soviet hands. Late in 1941 these pieces were issued to Red Army units to make up for the lack of anti-tank guns.
 * Several dozens of Polish guns fell into Soviet hands. Late in 1941 these pieces were issued to Red Army units to make up for the lack of anti-tank guns.