Captain - class frigate The Captain class was a designation given to 78 frigate s of the Royal Navy , constructed in the United States of America , launched in 1942 – 1943 and delivered to the United Kingdom under the provisions of the Lend - Lease agreement ( under which the United States of America supplied the United Kingdom and other Allied nations with materiel between 1941 and 1945 ) , they were drawn from two sub - classes of the American destroyer escort ( originally British destroyer escort ) classification : 32 from the " Evarts " sub - class and 46 from the " Buckley " sub - class . Upon reaching the UK the ships were substantially modified by the Royal Navy , making them distinct from the US Navy destroyer escort ships . Captain - class frigates acted in the roles of convoy escorts , anti - submarine warfare vessels , coastal forces control frigates and headquarters ships for the Normandy landings . 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 with 15 of the 78 Captain - class frigates being 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 " ) 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 . Naming . It was the intention of the Admiralty that these ships would be named after captain s that served with Vice - Admiral Horatio Nelson at the Battle of Trafalgar , but as building continued it became necessary to delve back further into history for the names of well - regarded admirals and captains . 66 of the 78 frigates bear names that had not previously been allocated to earlier Royal Navy ships . " Lawford " , " Louis " , " Manners " , " Moorsom " , " Mounsey " , " Narborough " , " Pasley " and " Seymour " had been previously used for destroyer s during World War I . " Rupert " was the fifth of that name since 1666 . " Torrington " was the fourth of that name since 1654 . " Holmes " had been used once before in 1671 , and " Fitzroy " had previously been used for a survey vessel in 1919 . Early history . In June 1941 His Majesty ' s 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 . The requested particulars were a length of , a speed of , a dual purpose main armament and an open bridge . The United States Navy had been looking into the feasibility of such a vessel since 1939 , and Captain E . L . Cochrane of the American Bureau of Shipping – who , during his visit to the United Kingdom in 1940 , had looked at Royal Navy corvette s and s – had come up with a design for such a vessel . This design anticipated a need for large numbers of this type of vessels , and had sought to remove the major production bottleneck for such vessels : reduction gearing required for the steam turbine machinery of destroyers . The production of reduction gears could not be easily increased , as the precision machinery required for their construction alone took over a year to produce . Therefore , a readily - available and proven layout of diesel - electric machinery , also used on submarines , was adopted . 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 . 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 five inch / 38 caliber gun – and replacing it with the three inch / 50 caliber gun , which allowed adding a superfiring third gun ( at the " B " position , forward ) , the original design specified eight engines for but other priority programs forced the use of only four with a consequent shortening of the hull and reducing the ships maximum speed by an estimated . The design had relatively light armour with for example the steel plate used on the Buckleys ranging from 1 / 2 inch to 7 / 16 inch with 1 / 4 inch plate being used for the majority of the hull and deck plating . The result was a vessel that could be produced quickly ( for example " Halsted " was built in just 24 and half days ) at half the cost of a fleet destroyer , ( $ 3 . 5 million compared to $ 10 . 4 million for a 1620 ton destroyer such as the Benson class or $ 6 . 4 million for a Hunt class destroyer ) 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 ( a plan to supply 1799 ships to the Royal Navy ) . The turbo - electric powered " Buckley " class were not part of the first order and were authorised later by Public Law 440 effective 6 February 1942 . The Royal Navy placed orders in November 1941 with four shipyards : the Boston Navy Yard , the Mare Island Navy Yard , the Philadelphia Naval Shipyard and the Puget Sound Navy Yard . When the United States entered the war , they too adopted the BDE design . The BDE designation was retained by the first six destroyer escorts ( BDEs 1 , 2 , 3 , 4 , 12 and 46 ) transferred to the United Kingdom . Of the initial 50 ordered , these were the only ones the Royal Navy received ; the rest were reclassified as destroyer escorts ( DE ) on 25 January 1943 and taken over by the United States Navy . By the end of World War II the Royal Navy had received 32 " Evarts " and 46 " Buckleys " from the Boston Navy Yard , Mare Island Navy Yard and Bethlehem - Hingham . The Royal Navy classified these ships as frigates , as they lacked the torpedo tube s needed for a destroyer classification . For those used to Admiralty - designed ships the Captains were unfamiliar : they had no break forward of the forecastle but instead had a graceful shear to deck - line from the forecastle to midship , and the " Evarts " had rakish cowls on top of the funnels . Those that served on these ships came to view these features as being very handsome . Amongst the differences with British - designed vessels were using bunks instead of hammocks and welds instead of rivets . Propulsion . The " Evarts " subclass had diesel - electric machinery , based on an arrangement used for submarines . There were two shafts . Four Winton 278A 16 - cylinder engines , with a combined rating of , drove General Electric Company ( GE ) generators ( 4 , 800 kW ) that supplied power to two GE electric motors , with an output of , for a speed of . It had been intended to provide another set of this machinery for an output of , to make the design speed of , but hull production greatly outstripped that of the machinery ; therefore , only one set of machinery was used per ship . In order to make the designed speed , the " Buckley " subclass had turbo - electric machinery . Two Foster - Wheeler Express " D " - type water - tube boilers supplied steam to GE steam turbines and generators ( 9 , 200 kW ) . Electric motors for drove the two shafts , each fitted with a three - bladed propeller of solid manganese - bronze that was in diameter . This all - electric drivetrain was considered particularly innovative at the time ( although the " Catherine " - class minesweepers had a similar arrangement ) . Royal Navy alterations . 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 . In all there were 109 items in the alterations and additions list for the " Evarts " and 94 for the " Buckleys " . One major design difference between the Royal Navy " Buckley " - class frigates and the US Navy " Buckley " - class destroyer escorts was that the " Buckley " class did not have the forward torpedo tubes fitted . ( The " Evarts " class was not designed to carry torpedoes . ) Further alterations were : Sea - keeping equipment . A crow ' s nest was affixed to the mainmast . A standard Royal Navy whaler was fitted on the port side of the funnel in addition to the US - issue ship ' s boat on the starboard side ; additional lifesaving rafts were also fitted : big ones on sloping launch skids aft of the funnel and small ones aft of the searchlights . 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 . Oiling fairlead s were fitted to the edge of the hull by the anchor winch . The bilge keels were lengthened and made deeper ( a process that took a minimum of three weeks ) . Gunnery . More 40 mm Bofors and Oerlikon guns were mounted in place of the removed torpedo tubes , and the MK IV elevating column Oerlikon mountings were replaced with the simpler MK V1A mountings ; those ships that were to serve as Coastal Forces control frigates hunting E - boats had extra guns fitted . On some ships , either gun shield s were fitted to the main armament , or a spray and blast shield was fitted to the B gun . Two - inch rocket flare projectors were fitted to the B gun : six if the spray and blast shield was fitted , three if not . A two pounder ( 40 mm ) " pom - pom " bowchaser was fitted to ships that were to serve as Coastal Forces control frigates . The bridge layout was significantly altered ; the biggest alteration was the addition of a two - tier director control tower that improved visibility and gave better protection to the equipment . Moreover , vertically fired " snowflake " parachute flare projectors were fitted to the bridge wing s . Anti - submarine . More depth charges were fitted on the upper deck of each side of the ship , allowing for about 200 in total ; Royal Navy smoke floats were fitted above the depth charges in addition to the US Navy chemical smoke cylinders fitted to the stern of the Captains . A medium frequency direction finding antenna ( MF / DF ) was fitted in front of the bridge and a high - frequency direction finding ( HF / DF , " Huffduff " ) Type FH 4 antenna was fitted on top of the mainmast ; furthermore , a radio - receiving set tuned to the frequencies used for ship - to - ship communication by German U - boats and E - boats was fitted and a German - speaking rating carried . The Captains were eventually given Type 144 series Asdic ( sonar ) sets , an upgrade from the original Type 128D , and a Foxer was fitted to the aft of the Captains ( and most other Atlantic escort vessels ) during 1944 to counter the new acoustic torpedoes . Navigation and communications . The steel parts around the binnacle ( the enclosure containing the compass ) were replaced by non - ferrous materials . In addition to the standard US Navy long - range position - fixing set ( LORAN ) , a Royal Navy short - range position - fixing set ( GEE ) was fitted . A radar interrogation system was installed that was able to challenge ships at sea ( only ships likewise fitted with the system would be able to reply ) , along with four coloured fighting lights ( signalling lamps installed on the yardarm to aid recognition by friendly forces during night fighting ) . Camouflage and insignia . Following standard Royal Navy protocols , all of the Captains had large pennant number s painted on the sides and stern of the hull , usually in blue , red or black . 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 ) . The ship ' s waterline was always in black . A total of five different camouflage schemes were employed on the Captains . The ships came from the shipyards in light grey with a few light blue stripes . 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 . Ships assigned to the English Channel in 1944 ( Coastal Forces control frigates and those assigned to Operation Neptune as headquarters ships ) received a design in black , blue , light grey and white . For ships assigned to the 16th Flotilla ( Harwich ) and 21st Flotilla ( Sheerness ) operating in the North Sea and English Channel , a scheme consisting of horizontal upper deck divisions of light and dark grey ( as used by the US Navy ) was used . 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 . Modifications to Normandy landing HQ ships . HMS " Dacres " , HMS " Kingsmill " and HMS " Lawford " were converted to headquarters ships for use during Operation Neptune ( the Normandy landings ) . These ships had their aft three - inch ( 76 mm ) gun and all the depth charge gear removed , and the superstructure extended , to provide accommodations for extra Staff Officer s ; two deckhouse s were built for the additional radios needed and a smaller extra mainmast was added to support the many additional aerials . Four more Oerlikons were fitted bringing the total to 16 , and a number of radar sets fitted ( Type 271 centimetric target identification and Type 291 air warning , and the associated Types 242 and 253 IFF sets ) . The complement was reduced to 141 , but with a headquarters staff of 64 . Ships ' companies . The Captains had a typical crew of either 156 ( " Evarts " ) or 186 ( " Buckley " ) officers and ratings . The bulk of the ratings enlisted after the outbreak of World War II , thus having little military or seafaring experience , and had to be trained in whichever branch of the Navy they chose to serve ; after about six weeks drilling , marching and generally getting physically fit they went into specific job training . Many of the senior non - commissioned officer s were pre - war Royal Navy ratings who had been promoted . Engineering personnel were faced with the added complication of power plants not normally found in the Royal Navy . Initially , they were trained alongside US Navy personnel at purpose - built facilities in the General Electric Company factories at Cleveland and Syracuse , and were awarded certificates at the end of their training ; later , training was provided in the United Kingdom . Ship ' s companies were shipped over to the USA by them taking passage from the Clyde or Liverpool to New York on liners such as the " Queen Mary " . On arriving in New York , the crews were initially assigned to HMS " Saker " until they were reassigned to a Captain - class frigate . Later , some of the Captains were ferried across the Atlantic by crews of the Royal Canadian Navy coming to the United Kingdom to collect frigates ordered by the Canadians . Operations . These ships were primarily deployed to escort groups that were then used to provide anti - submarine cover to the convoys that they escorted . The four or more ships in an escort group , by operating together under a single commander , were able to use group tactics so that with the issue of a single short command the various ships of the group , often out of sight of each other , could be relied upon to act in a co - ordinated fashion . A small number of Captains were converted to act as headquarters ships during Operation Neptune ( the Normandy landings ) and as coastal forces control frigates . Captains that operated with Coastal Forces ( motor torpedo boat s , motor gun boat s and US Navy PT boat s ) sank at least two two - man submarines , and were involved in the destruction of at least 26 E - boats , one KFK patrol vessel ( coastal escort vessels constructed so as to resemble a fishing - vessel ) , two minesweepers , and the shooting down of a Junkers Ju 88 aeroplane . 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 , they also during the course of World War II collectively destroyed more German submarines than any other Royal Navy ship class . Post war . 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 . The last of the Captains returned was " Hotham " , which in the post - war period served as a floating power station in Singapore until early 1948 , when she sailed for Portsmouth , becoming the base for a Royal Navy Engineering research team experimenting with gas turbine engines . " Hotham " was returned on 25 April 1952 and simultaneously transferred back to the United Kingdom under the Mutual Defence Assistance Program . The partially stripped vessel was returned to United States custody on 13 March 1956 . In Film . Much of the Robert Mitchum film " The Enemy Below " ( 1957 ) was filmed in , a " Buckley " - class DE , of the same type as the " Captain " - class . The rest of the film is set in the U - boat that it is hunting . Memorial . On 17 April 2005 a memorial to the Captain class , those that served and those killed in action while serving in them was dedicated at the National Memorial Arboretum near Alrewas , Staffordshire .