Mid-Ocean Escort Force (MOEF) referred to the organisation ofanti-submarine escorts forWorld War II tradeconvoys between Canada and Newfoundland, and theBritish Isles. The allocation of United States, British and Canadian escorts to these convoys reflected preferences of the United States upon United States' declaration of war and the organisation persisted through the winter of 1942–43 despite withdrawal of United States ships from theescort groups. By the summer of 1943, United States Atlantic escorts were focused on the fasterCU convoys and theUG convoys between Chesapeake Bay and the Mediterranean Sea; and only British and Canadian escorts remained on theHX,SC andON convoys.
On the basis of experience duringWorld War I, theAdmiralty instituted trade convoys in United Kingdom coastal waters from September 1939.[1]Anti-submarine escorts were allocated on the basis of perceived threat. EarlyGerman Type II submarines from bases in Germany were unable to operate effectively beyond European coastal waters. Following acquisition of bases inNorway and France,German Type IX submarines andGerman Type VII submarines refuelled byGerman Type XIV submarines operated in the mid-Atlantic beyond the range of patrolling aircraft. Many anti-submarine escorts lacked the endurance to accompany convoys through the mid-Atlantic. HX 129 left Halifax on 27 May 1941 as the first convoy to receive escort for the entire trip.[2] Escorts based inHalifax Harbour handed HX 129 off to escorts based inNewfoundland who subsequently transferred HX 129 to escorts based inIceland who in turn delivered HX 129 to escorts based in theWestern Approaches.
In Newfoundland on 9 August 1941, PresidentFranklin D. Roosevelt agreed to provide American destroyers for the Canada to Iceland portion ofHX convoys and westboundON convoys.[3] HX 150 sailed 16 September 1941 as the first convoy with American escort.[4] ON 18 sailed 24 September as the first westbound convoy with American escort.[5] TheRoyal Canadian Navy continued to escort theSC convoys and their slower ON counterparts.[6] Canadian escort groups were increased from a nominal strength of four ships to six – typically oneCanadian River-class destroyer with fiveFlower-classcorvettes.[7]
TheGleaves-class destroyerKearny was torpedoed while escortingConvoy SC 48 on 17 October 1941.[8]Clemson-class destroyerReuben James was torpedoed and sunk on 31 October 1941 while escortingConvoy HX 156.[9] When the United States declared war, American escort groups typically contained five destroyers, although sixUnited States Coast GuardTreasury-class cutters were included within the pool of ships rotating in and out of these escort groups.[10]
As the United States Navy struggled to find enough destroyers to meet escort needs for both the Pacific and the vulnerable Atlantic coastal shipping, the shortergreat-circle route from Newfoundland to theBritish Isles was considered as a means of eliminating meeting point delays and reducing the number of destroyers required for escort of convoys between Canada and the United Kingdom. Initial proposals by the United States on 24 January 1942 produced an agreement in early February for a mid-ocean escort force organisation of fourteen escort groups.[11] American-led escort groups were prefixed with the letter "A"; while "B" indicated British-led escort groups and "C" designated Canadian-led escort groups. Fifteen United States destroyers, fifteen Royal Navy destroyers and twelve Canadian destroyers were to provide the striking power of these escort groups while 52 British and 49 Canadian Flower-class corvettes were to perform the patrolling role. Approximately one-third of the theoretical MOEF escort group strength of three destroyers and seven corvettes was unavailable at any given time.[12] Half of the unavailable ships needed storm or battle damage repairs,[13] and the remainder were undergoing normal refit and training.
Each MOEF escort group worked in a 33-day cycle allowing nine and one-half days with a westbound ON convoy, six days inSt. John's, Newfoundland and Labrador, nine and one-half days with an eastbound HX or SC convoy, and eight days' refit inDerry.[14] The shorter routing away from Iceland eliminated the need for most escorts to attempt maintenance in Iceland's poorly equippedHvalfjörður anchorage; but the United States was required to maintain an additional force of five destroyers in Iceland to escort ships between trans-Atlantic convoys and United States military occupation bases. The Royal Navy continued to provide an eastern local escort force ofnaval trawlers in the Western Approaches while Canada continued to provide awestern local escort force (WLEF) of corvettes, minesweepers, and short-range destroyers between Halifax Harbour and Newfoundland.[15]
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Corvettes had adequate endurance for MOEF assignments, but the fuel economy of destroyers was poor at the speeds that convoys operated. The escort group leaders were modern destroyers with adequate endurance but, of the older destroyers allocated to trade convoy escort, only theClemson subgroup of the Town-class destroyers proved suitable for MOEF assignments.[17]Wickes-class destroyers were useful for the Canadian WLEF and the American Iceland shuttle; but lacked endurance to stay with a trade convoy for the full distance covered by the MOEF Escort Groups. TheAdmiralty converted some V and W-class destroyers to long range escorts by removing the forward boiler and using the space for additional fuel tanks.[18]
Nineteen modern American destroyers left the Atlantic to escort thebattleshipsNew Mexico,Mississippi,Idaho, andNorth Carolina and theaircraft carriersYorktown,Wasp, andHornet to the Pacific.[19] The remaining American destroyers were diverted from MOEF assignments to troop convoys and in response to theU-boat'sSecond happy time off the American east coast.[20] Escort Groups A-1 and A-2 were disbanded when their modern Americandestroyer leaders were assigned elsewhere. Escort Groups A-4 and A-5 were redesignated B6 and B7, respectively, when the Royal Navy assignedF-class destroyersFame andFiredrake as leaders.[21] Escort Group B5 was reassigned to Caribbean trade convoys in March 1942.[16] Beginning in April, the following eleven groups escorted HX convoys, SC convoys and ON convoys through the winter of 1942–43:
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Gleaves-class destroyerGleaves left the escort group after convoy ON 92 lost seven ships.[23] USCG Treasury-class cuttersSpencer andCampbell assumed escort leader responsibility. Flower-class corvettesMayflower andTrillium replaced Flower-class corvettesChilliwack,Shediac andAlgoma.[24]
Flower-class corvetteDianthus replaced Flower-class corvettesMayflower andBittersweet.[24]
Flower-class corvetteDauphin rotated into the group.[24]
The escort group was then redesignated C-5 under Canadian command after the USCG Treasury-class cutters were reassigned for conversion to amphibious force flagships.[34]
Flower-class corvettesBorage,Meadowsweet andWallflower joined the group; andVenomous was replaced by the long-range W-class escortWatchman.[35] Convoys HX 187, ON 96, HX 193, ON 108, SC 92, ON 119, HX 201, ON 124, HX 206, ON 134, SC 105, HX 215, ON 151, SC 114, ON 162, SC 119, ON 171 and HX 230 were escorted without loss.[31] Convoy ON 178 lost three ships torpedoed byU-415 andU-191.[36]
Flower-class corvettesCampanula,Heather andMignonette joined the group; and the low-endurance destroyersLeamington andVeteran were replaced by long-range V and W-class escortsVanessa andWhitehall.[35] Convoys SC 81, ON 97, SC 86, ON 107, HX 198, ON 118, HX 203, ON 128, HX 208, ON 138, HX 213, ON 148, HX 219 and ON 159 were escorted without loss.[31]Convoy SC 118 lost eight ships.[32] Convoys ON 170, SC 123 and ONS 4 were escorted without loss.[37]
Low-endurance destroyersGeorgetown andBulldog were replaced by the E-class destroyerEscapade and the Polish destroyersBurza andGarland.[35] Flower-class corvetteOrchis replacedHeartsease and the four corvettes with Free French crews (Aconit,Lobelia,Renoncule andRoselys) were assigned to this group.[35] Convoys HX 188, ON 98, HX 194, ON 110, SC 93, ON 121, HX 202, ON 126, HX 207, ON 136, SC 106, ON 146, HX 218, ON 157 and SC 117 were escorted without loss.[31] Convoy ON 167 lost two ships.[28]Convoy HX 228 lost four ships torpedoed byU-221,U-757 andU-444.[38]U-444 was rammed by the group leaderHarvester.[38]Harvester was then torpedoed byU-432.[38]U-432 was then sunk byAconit.[38]Thornycroft type leaderKeppel was assigned as group leader replacement.[36] Convoy ON 174 was escorted without loss.[39] Convoy HX 232 lost three ships torpedoed byU-563 andU-168.[36]
Flower-class corvettesAbelia,Clover andSnowflake joined the group; and the low-endurance destroyerRoxborough was replaced by the Town-class destroyerBeverley.[35] Convoys SC 82, ON 99, SC 87, ON 109, HX 199, ON 120, HX 204 and ON 130 were escorted without loss.[31] Convoy HX 209 lost one ship torpedoed byU-254.[40] Convoys ON 140, HX 214, ON 150, HX 220, ON 161 and ON 169 were escorted without loss.[26]Convoy HX 229 lost twelve ships.[28] Convoy ON 176 lost one ship andBeverley was torpedoed byU-188.[41] Convoy HX 234 lost one ship torpedoed byU-306.[36]
The Royal Norwegian Navy-crewed Flower-class corvettesAndenes,Eglantine,Rose,Potentilla, andMontbretia from Escort Group A4, and the new leader F-class destroyerFame were joined by the V-classViscount (which had been reconstructed as a long range escort), the Town-class destroyerRamsey, and the British Flower-class corvettesKingcup andVervain.[35] Convoys SC 83, ON 101, SC 88, ON 111 and HX 200 were escorted without loss.[31]Convoy ON 122 lost four ships torpedoed byU-605,U-176 andU-438.[27] Convoys HX 205 and ON 132 were escorted without loss.[26]Convoy SC 104 lost seven ships.[32]Convoy ON 144 lost five ships torpedoed byU-264,U-184 andU-624.[42]Montbretia was torpedoed byU-262.[42] Convoy HX 217 lost two ships torpedoed byU-524 andU-553.[43] Convoys ON 155, SC 116, ON 165, HX 227, ONS 1 and SC 125 were escorted without loss.[44]
The Flower-class corvetteLoosestrife from Escort Group A-5, and the new leader F-class destroyerFiredrake were joined by the Town-class destroyersChesterfield andRipley and by the Flower-class corvettesAlisma,Coreopsis,Jonquil,Pink andSunflower.[35] Convoys HX 186, ON 94, HX 192, ON 106, SC 91, ON 117, SC 103, ON 142 and HX 216 were escorted without loss.[31] Convoy ON 153 lost three ships torpedoed byU-610,U-356 andU-621.[45] On 17 December 1942 HMSFiredrake was torpedoed byU-211 and sank.[45] TheD-class destroyerHMS Duncan was assigned as replacement group leader;[46] and the newRiver-class frigateTay joined the group.[47] Convoys SC 115, ON 164, SC 120 and ON 173 were escorted without loss.[48] Convoy HX 231 lost three ships torpedoed byU-635,U-630 andU-706.[49]Convoy ONS 5 lost eleven ships.[50]
CorvetteBuctouche was replaced by Flower-class corvettesBattleford,Chilliwack,Orillia andPrimrose.[51] Convoy HX 189 was escorted without loss.[22] Convoy ON 100 lost three ships torpedoed byU-94 andU-124.[25] Convoys HX 195 and ON 112 were escorted without loss.[26]Convoy SC 94 lost ten ships.[32] Group leaderAssiniboine and Flower-class corvettesDianthus,Nasturtium andPrimrose were replaced by destroyerSt. Laurent and Flower-class corvettesEyebright,Napanee,Kenogami andShediac.[51] Convoys ON 123, SC 99, ON 133, HX 211, ON 143 and SC 110 were escorted without loss.[31] Flower-class corvettesOrillia,Chambly andEyebright rotated out of the group.[52]Convoy ON 154 lost thirteen ships.[28] Convoy HX 222 lost one ship torpedoed byU-268.[53] Flower-class corvetteChilliwack was replaced by new River-class frigateItchen.[52] Convoys ONS 2 and SC 127 were escorted without loss.[54]
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Convoys SC 84, ON 103 and SC 89 were escorted without loss.[55] DestroyerBurnham replaced destroyerSt. Laurent; and Flower-class corvetteDauphin joined the group.[56] Convoy ON 113 lost three ships torpedoed byU-552,U-607 andU-132 while Town-class destroyerSt. Croix sankU-90.[57] Convoys HX 201 and ON 119 were escorted without loss.[26] Convoy SC 97 lost two ships torpedoed byU-609 whileMorden sankU-756.[58] Convoys ON 129 and SC 102 were escorted without loss.[55] DestroyerSherwood replaced destroyerBurnham; and Flower-class corvettesPictou andPrimrose replaced Flower-class corvettesDauphin andBrandon.[56] Convoy ON 139 lost two ships torpedoed byU-443.[53] Flower-class corvetteOrillia joined the group.[56] Convoys SC 108, ON 149 and SC 113 were escorted without loss.[55] New River-class frigatesLagan andWaveney joined the group.[56] Convoys ON 160, HX 225 and ON 179 were escorted without loss.[26]
Convoys ON 93, HX 191, ON 104 and SC 90 were escorted without loss.[31] Flower-class corvetteCamrose was replaced by corvetteAgassiz.[59] Convoy ON 115 lost two ships torpedoed byU-552 andU-553 whileSkeena and Flower-class corvetteWetaskiwin sankU-588.[60] Convoys HX 202, ON 121, SC 98, ON 131, HX 210 and ON 141 were escorted without loss.[31] Convoy SC 109 lost one ship torpedoed byU-43 andSaguenay was irreparably damaged when depth charges blew off its stern following a collision.[30] Town-class destroyerBurnham replacedSaguenay. Flower-class corvettesWetaskiwin,Sackville,Galt andAgassiz were replaced by corvettesBittersweet,Eyebright,La Malbaie andMayflower. The new River-class frigateJed joined the group.[59] Convoys ON 152, HX 221, ON 163, HX 226, ON 172, SC 124 and ON 180 were escorted without loss.[61]
Convoys ON 95, SC 85, ON 105, HX 197, ON 116 and SC 96 were escorted without loss.[31] DestroyerSt. Francis was replaced by Town-class destroyerSt. Croix and Flower-class corvettesLethbridge,Prescott andEyebright were replaced by corvettesAmherst,Celandine andSherbrooke.[62]Convoy ON 127 lost six ships;[28] andOttawa was torpedoed byU-91.[63] Convoys SC 101 and ON 137 were escorted without loss.[55]Convoy SC 107 lost fifteen ships.[32] DestroyerSt. Croix was replaced by Town-class destroyerChurchill and Flower-class corvetteArvida was replaced by corvettesBrandon andCollingwood.[62] Convoys ON 147, SC 112 and ON 158 were escorted without loss.[55] Convoy HX 224 lost two ships torpedoed byU-456.[64] Convoys ON 177 and HX 235 were escorted without loss.[65]
Escort Group B-5 returned to MOEF with the H-class destroyerHavelock, the Flower-class corvettesPimpernel,Godetia,Saxifrage,Buttercup andLavender and with the new River-class frigateSwale replacing the old destroyers.[66] Convoy ON 168 was escorted without loss.[39]Convoy SC 122 lost eight ships.[32] Convoy SC 126 was escorted without loss.[32]
River-class frigates brought two significant advantages to MOEF. Their numbers allowed the older escorts time to refit with modern sensors like 10-centimetreradar and modern anti-submarine weapons like theHedgehog projector. Destroyers replaced by new frigates were formed into mobile support groups able to move rapidly to convoys coming under attack.[67] Through 1943, newescort carriers became available to increase the surveillance capability of support groups.[68] As the winter weather cleared, new Very Long RangeConsolidated B-24 Liberator patrol bombers extended surveillance into the mid-Atlantic.[69]