The Thompson M1A1 is a submachine issued mostly to U.S. NCO's during WW2. It was also given to other countries such as Britain under the Lend-Lease policy, but in less numbers than the M1928A1. It has a high fire rate but high recoil. It was used more in the hands of the U.S. than the M1928A1, being cheaper to make.
It is the second weakest submachine gun in Arcade Mode the first being the Thompson M1928A1.