The submachine gun, which was much favored by «violin carrying gangsters» of the Capone-gang era, was invented by John Taliaferro Thompson (1860-1940), collaborating with other inventors, notably Navy Commander John N. Blish. Tommy gun is a nickname for the Thompson submachine gun, a name not generally used.
At first, the U.S. Army displayed little interest in the gun, although its use for close combat was particularly effective. But it did receive some use and favorable reactions during World War II. The gun is portable, weighing from six to twelve pounds, and its clips can hold twenty to fifty shots. It has a pistol grip and shoulder stock for firing from the shoulder, but it was more often fired from the hip. The cinemas depicting the period of warfare by Prohibition-type gangsters always showed them shooting from the hip — spraying the area, so to speak. But the gun was not easily mastered because it had a decided tendency to ride up. The gun had to be locked in place or else the shots would go over the head of the target.
Cyril Leslie Beeching reports: «The notorious ‘Saint Valentine’s Day Massacre’ in 1919, when seven members of the Moran gang were gunned down in a Chicago garage, is believed to have been carried out by A1 Capone’s men (posing as policemen), using sawed-off shotguns and tommy-guns».