Unit History: HM Submarines

HM Submarine X1 was conceived and designed as a submersible commerce raider for the Royal Navy, and at the time of her launching was the largest submarine in the world. The idea of a submarine cruiser had been mooted as early as 1915, but was not put into practice until 1921.
 
X1, which was based on the uncompleted German U-173 class, was laid down on November 2 1921 at the Naval Dockyard Chatham and completed on September 23 1925, commissioning in December 1925.
 
The 1922 Washington Naval Treaty, of which Britain was a signatory, did not ban submarines but it did ban their use against merchant ships, which was X1’s unacknowledged purpose; its armament had been designed to successfully engage the classes of vessels likely to be escorting convoys, such as destroyers and frigates. Therefore, a certain amount of secrecy surrounded X1, the government even going to the lengths of taking a national newspaper to court over its pictures of the new submarine following her launch, all copies of the paper being seized.