 The term "frigate" was readopted during the Second World War by the British Royal Navy to describe an anti-submarine escort vessel that was larger than a corvette, while smaller than a destroyer.Equal in size and capability to the American destroyer escort, frigates are usually less expensive to build and maintain.Anti-submarine escorts had previously been classified as sloops by the Royal Navy, and the s of 1939–1945 were as large as the new types of frigate, and more heavily armed.