Interwar development ran from earlier sloops through the Bittern, Egret, and Black Swan classes. Treaty rules allowed vessels of up to 2,000 tons and 20 knots without torpedoes, a category the sloop fitted neatly. At normal convoy speeds these ships remained in the range where ASDIC had the best chance of working. Turbine supply and budgets constrained how many could be built, and wartime demand pushed simpler corvettes and frigates into the same broad mission.
Chapter · 23:39-26:14
Sloops as long-range anti-submarine convoy escorts
The sloop was a specialist long-range escort: modestly sized, treaty-compatible, and designed to search at speeds where ASDIC was useful.