The 152 mm howitzer-gun M1937 (ML-20) was a Soviet gun-howitzer. The gun was developed by the design bureau of the plant no 172, headed by F. F. Petrov, as a deep upgrade of the 152-mm gun M1910/34, in turn based on  the 152-mm siege gun M1910, a pre-World War I design by Schneider. It  was in production from 1937 to 1946. The ML-20 saw action in World War  II, mainly as a corps / army level artillery piece of the Soviet  Army.Post World War II, the ML-20 saw combat in numerous conflicts  during the mid to late twentieth century.