The Tommy Gun: World War I Army Brigadier Gen. John Taliaferro Thompson invented what came to be known as the Tommy Gun. Went into production in 1921. The U.S. Marines first used the Tommy gun in Nicaragua in 1925, where it excelled in jungle fighting. Before gun permits were required, customers could buy them from hardware stores.
Winston Churchill squints as he test fires an American M1928 Thompson submachine gun, many of which were supplied to England under the Lend-Lease program. Note the unusual hybrid forestock with both descending pistol and horizontal hand grips ~