Tanks first began rolling over the battle fields during the First World War. It was a new development and a new threat to counter. Rifles and machine guns had no effect on these steel monsters. A new need arose for antitank weapons, and directly after the war, Bofors began planning for infantry support guns, as the early antitank weapons were called.
Bofors developed three different 37 and 47 mm calibre infantry support guns during the years 1921–1924. They were tested in Switzerland and Poland but the guns were never exported. The company also invested in a combination weapon in the form of one 75 mm barrel and one with 47 mm mounted on the same carriage. This weapon, as well as another variant, was sold to Siam (Thailand) and China.
It was only at the beginning of the 1930s that the Swedish Army decided on the type of antitank weapon they wanted: a 37 mm antitank gun. It could be moved by hand within smaller areas and pulled by a horse or motor vehicle over longer distances. Before and during the Second World War, Bofors delivered a total of about 650 of these guns to the Swedish Army. They were also exported to Poland and England.