The Thompson SMG was a submachine gun invented in 1919 by General John T. Thompson. It was widely used by chicago gangsters during the prohibition era. It had several nicknames, such as "tommy gun" and "chicago typewriter." The thompson fires about 1,000 .45 ACP pistol rounds per minute (600-1200 rounds depending on the model). It started to be replaced by the M3 SMG as the standard infantry submachine gun in 1944. However, it continued service until the Korean War.