The term ARM OF THE BRITISH MILITARY can be summarized by two crossword solutions: STEN (4 letters) and STENGUN (7 letters). STEN is a family of British submachine guns that were used extensively by the British military during World War II. The STEN gun was a simple, cheap, and reliable weapon that could be mass-produced quickly. The STENGUN is a variant of the STEN gun that was designed for use by paratroopers and special forces. It was lighter and more compact than the original STEN gun, making it easier to carry and use in tight spaces. Both the STEN and STENGUN were important weapons in the British military's arsenal during World War II.