During the course of World War II this class participated in the sinking of at least 34 German submarines and a number of other hostile craft; 15 of the 78 Captain-class frigates were either sunk or written off as a constructive total loss.

In the post-war period, all of the surviving Captain-class frigates except one (HMS Hotham which was used as a power station and for powerplant experiments) were returned to the US Navy before the end of 1947 in order to reduce the amount payable under the provisions of the Lend-Lease agreement; the last Captain-class frigate was returned to United States custody in March 1956.

[1] In June 1941 the British government, seeking to take advantage of the US Lend-Lease program, asked the United States to design, build and supply an escort vessel that was suitable for anti-submarine warfare in deep open ocean situations.

[2] The requested particulars were a length of 300 feet (90 m), a speed of 20 knots (37 km/h), a dual purpose main armament and an open bridge.

When the United Kingdom made its request, Admiral Stark of the US Navy decided to put these plans into motion and recommended that the British order be approved.

[6] Gibbs and Cox, the marine architects charged with creating working plans, had to make several alterations to the production methods and to Captain Cochrane's original design, most notably dropping another production bottleneck – the 5-inch/38-caliber gun – and replacing it with the 3-inch/50-caliber gun, which allowed adding a superfiring third gun (at the "B" position, forward);[3] also, the original design specified eight engines for 24 knots (44 km/h; 28 mph) but other priority programs forced the use of only four with a consequent shortening of the hull and reduction of the ship's maximum speed by an estimated 4 knots (7.4 km/h; 4.6 mph).

[12]) On 15 August 1941 President Franklin D. Roosevelt authorised the construction of 50 of the new Evarts-class design as BDE 1–50 (British destroyer escort) as part of the 1799 program.

[19] Electric motors for 12,000 shp (8,900 kW) drove the two shafts, each fitted with a three-bladed propeller of solid manganese-bronze that was 8 ft 6 in (2.59 m) in diameter.

The first port of call in the United Kingdom for most of the Captain-class vessels was Pollock Dock, Belfast where the ships were modified in order to match Admiralty requirements.

The problem was ultimately addressed by increasing the number of depth charges stowed on the upper deck and fitting larger bilge keels, which tamed the roll to manageable levels.

[24] A standard Royal Navy 27-foot (8 m) whaler was fitted on the port side of the funnel in addition to the US-issue ship's boat on the starboard side;[25] additional Carley lifesaving rafts were also fitted: big ones on sloping launch skids aft of the funnel and small ones aft of the searchlights.

[26] Wind deflectors were fitted on the leading edge of the bridge area and a canvas-covered shelter was installed on the quarterdeck to provide better weather protection for depth charge crews.

[24] A 40 mm QF 2-pounder Mk VIII "pom-pom" was fitted as bowchaser to ships that were to serve as Coastal Forces control frigates.

Following standard Royal Navy protocols, all of the Captains had large pennant numbers painted on the sides and stern of the hull, usually in blue, red or black.

[33][34] The escort groups to which most Captains were assigned had their own individual insignia; these distinctive and colourful designs were painted on the side of the ship's funnel, and if the ship was home to the escort group's senior officer it would also have a coloured band painted around the top of the funnel (usually in blue or red).

[35] For those ships assigned to the North Atlantic, a scheme consisting of light and dark blues and greens with some soft white was adopted as it was believed that this would blend with the sea colour in bad weather.

[30] Early in 1945, a scheme was adopted that was to be common to all Royal Navy ships, consisting of white with a sky-blue stripe along the hull.

[40][page needed] A small number of Captains were converted to act as headquarters ships during Operation Neptune (the Normandy landings) and as coastal forces control frigates.

[44] Collectively, the Captain class gained battle honours for service in Arctic (Russian) Convoys, Atlantic, Biscay, English Channel, Normandy (D-Day on 6 June 1944 and subsequent related operations), North Foreland and Walcheren.

[80] At the end of World War II, most of the surviving Captains were returned to the US Navy as quickly as possible to reduce the amount payable under the provisions of the Lend-Lease agreement.

[81] Hotham was returned on 25 April 1952 and simultaneously transferred back to the United Kingdom under the Mutual Defence Assistance Program.