Czechoslovakia’s support for the Little Entente countries had a major impact on their armaments. During the interwar period, Yugoslavia and Romania purchased infantry weapons from the Czechoslovak Arms Factory in Brno. Efforts to promote ZB machine guns in the Yugoslav army resulted both in the supply of ZB 26 light machine guns from the early days of their production, and mainly in the development of the ZB 30J machine gun, where the last letter in the designation stood for Yugoslavia (Jugoslávie in Czech).
On 30 July 1936, the arms factory entered into a secret contract with the Yugoslav military administration for the supply of 10,000 ZB 30J machine guns, which included a licence for their production and a free exchange for 5,000 old ZB 26 machine guns, so that the factory was to supply a total of 15,000 new weapons.
The production of machine guns for Yugoslavia started at the end of 1936. In December 1937, the factory shipped the first 5,000 machine guns, introduced in the Yugoslav army under the designation M 37. By the end of February 1938, a total of 10,000 machine guns had been shipped to Kragujevac, and the remaining amount went to Yugoslavia in June 1938.