HMCS Ypres was one of 12 Battle class trawlers used by the Royal Canadian Navy (RCN). Named after the Second and Third battles of Ypres, she was built by Polson Iron Works, in Toronto, Ontario, and was commissioned on 13 November 1917. Like many of the RCN's Battle class trawlers, Ypres was decommissioned in 1920. After being recommissioned on 1 May 1923 as a training ship, in November 1932 she was again decommissioned and was placed in reserve. Refitted as a gate vessel in 1938 and recommissioned, Ypres, designated Gate Vessel 1, formed part of the Halifax boom defences until 12 May 1940, when she was accidentally rammed and sunk by the British battleship HMS Revenge, but without loss of life. After this incident, the crews of other gate vessels would pretend to make elaborate preparation