The S/T/U/V/W-classes were the intermediate Emergency flotillas (numbered from the 5th to the 9th) of the War Emergency Programme. The main difference from the preceding classes was the inclusion of a new mount for the 4.7-in QF Mk. IX guns which provided increased elevation (the exception was HMS Savage which would introduce an experimental 4.5-in twin mounting that would later be the standard on the Battle class destroyers). Anti-aircraft armament varied among the ships but was notable for introducing a stabilized, triaxial 40-mm Bofors in exchange for the 2-pdr guns of previous glasses. By the end of war, this armament consisted of up to five Bofors and 12 20-mm guns, while the maximum number of depth charges that could be carried was 130. Other changes compared to previous classes were a lattice foremast introduced in the T-class, and a Mark III(W) director in the W-class. A total of 40 ships of these five classes were built, of which only four ships were sunk in combat during World War II; relatively mild casualties compared to some of the pre-war classes. Two ships were completed for Canada and another two for Norway, while post-war transfers were provided for the Netherlands, Yugoslavia, and South Africa. Almost all of the remaining Royal Navy ships (as well as one of the Canadian ships) were converted after the war to Type 15 or Type 16 anti-submarine frigates where they served into the 1960s and 70s.

Ships of these classes began entering service with the Royal Navy and Allied navies from mid-1943 onward. As such, they avoided the more hostile conditions in the Mediterranean and Atlantic which helped reduce casualties. Most ships served with either the Home or Mediterranean fleets, escorting some of the Allied invasion forces as well as the Arctic convoys. Notably, the HNoMS Svenner was sunk by German torpedo boats during D-Day; the largest warship sunk in action that day. HMS Swift was also lost off Normandy by a mine later in the same month. HMS Hardy was sunk in the Barents Sea by a U-boat, while HMS Saumarez was damaged by a mine post-war in the Corfu Channel and never repaired. Numerous ships served in the British Pacific Fleet, of which HMS Verulam, HMS Venus, HMS Vigilant and HMS Virago were notable for ambushing the Japanese heavy cruiser Harugo in the Battle of the Malacca Strait. Most ships were paid off or placed in reserve after the war before converted to frigates.