In the 1930s, the Swedish 40 mm Bofors anti-aircraft cannon rose to world fame as an anti-aircraft weapon for both the navy and the army. Before the outbreak of World War II, AB Bofors had already sold this weapon system to 17 countries, including Finland.

The first nine 40 mm anti-aircraft cannons arrived in Finland in spring 1939. Eight of these were issued to anti-aircraft units and one was transferred to the State Cannon Factory (Valtion Tykkitehdas) in Jyväskylä to serve as a model cannon. Immediately after personnel training, the first live-fire exercise was conducted in summer 1939 at Camp Muurila on the Karelian Isthmus. During October–November 1939, Finland managed to purchase an additional 56 cannons from AB Bofors, establishing a total of eight light anti-aircraft batteries with 40 mm Bofors cannons before the Winter War. During the Winter War, Finland bought another 36 cannons from Bofors and during the so-called interim peace as many as 130 cannons from Germany. At the beginning of the Continuation War in 1941, the first 20 cannons manufactured at the State Cannon Factory were also deployed, followed by a further 35 cannons in 1942 and 16 cannons in 1944. The anti-aircraft tanks purchased from Sweden in 1942 were also armed with Bofors 40 mm cannons. In all, the army had 278 Bofors cannons in service during the two wars.

The 40 mm Bofors cannon proved to be worthy of its reputation. In the Winter War, these Bofors cannons destroyed 128 enemy planes, and the total number of enemy planes shot down with this cannon in both the Winter and Continuation War was more than 500.

Conscript training with the 40 mm cannon was discontinued in 1986, and the equipment was decommissioned in 1992. Some of the Bofors cannons were modernised in the early 1960s (40 ItK/36-59). These were decommissioned in 2000.

40 ItK/36-39 Bofors

Manufacturer: AB Bofors, Sweden, and several others by licence

Calibre:                                                      40 mm

Muzzle velocity:                                                               800 m/s

Rate of fire:                                                120 rounds per minute

Effective range:                                          2500 m

Travelling weight:                 2100 kg

Firing weight:                       2000 kg