The Soviet Union started to develop anti-tank guns in the late 1920s. These attempts failed to advance beyond early stages as Soviet engineers lacked experience with this type of weapon. To solve this problem the USSR received assistance from Germany. The Treaty of Versailles forbade Germany to have anti-tank artillery, but Rheinmetall secretly continued to work on anti-tank guns and in 1926 built a pre-production sample of a new 3.7 cm gun model 26. For their part the Germans were interested in any opportunity to proceed with development of this and other types of weapons.