Following the Dunkirk evacuation in 1940, the Royal Air Force decided it required a submachine gun for airfield defence. With no time available for the usual research and development of a new weapon, it was decided to create a direct copy of the German MP 28. The British Admiralty decided to join with the RAF in adopting the new weapon, and played a key role in its design. Ultimately, it was within the Royal Navy that most of the Lanchesters that were produced went into service.