Contrarily to destroyers, escort ships did not appear as a type until the development of the submarine threat against merchant
ships during the First World War. They were built in large quantities but they were ineffective due to the primitive hydrophones and the lack of
adequate antisubmarine weapons. Around 1936, with the incoming danger of war, plans were made for a new generation of escort ships which should
deal with the already important threat posed by submarines and aircraft. To face this situation were introduced corvettes armed with antiaircraft
cannons and depth charges. Some of these ships were also intended for mine laying and others even for mine sweeping.
However, corvettes had the defect of insufficient speed, operational range and storage space for the charges, being inadequate to sustain the long
missions that German submarines imposed on the Royal Navy. The corvettes of the Castle class were the last ones built during the war, being eclipsed by
the larger frigates, of superior qualities. Along with aircraft, escort ships were crucial to keep open the routes of the convoys; without them the Allies
could not have sustained the war effort. Italy and Japan built during the war small antisubmarine ships, but none of these countries managed to build
them in the required amounts nor with enough technical qualities to deter the submarine attacks against their convoys. This was a determinant
factor for their defeat.
British antisubmarine corvette HMS Hedingham Castle circa 1950
British minesweeper corvette of the Algerine class during Second World War
Italian antisubmarine corvette Baionetta during Second World War
Soviet antisubmarine corvette of the Grisha II class circa 1975
Soviet missile corvette of the Nanuchka I class circa 1975