SL convoys

Based on World War I experience, SL convoys were one of four trade convoy routes organized at the beginning of the Battle of the Atlantic. The other routes were HX convoys from North America, HG convoys from the Mediterranean, and a short-lived series of HN convoys from Norway. Eight ships sailed as convoy SL 1 on 14 September 1939 and three faster ships sailed six days later as a faster section -- sometimes designated SL(F) 1 or SL 1(F). The slower convoy was sometimes similarly suffixed with an (S). Early convoys were usually accompanied by an armed merchant cruiser or one of the South Atlantic Station cruisers based at Freetown; but no anti-submarine screen was provided until the slower and faster sections rendezvoused with a single Escort Group in the Southwest Approaches. Freetown was little more than a protected anchorage, with no shore facilities. The town had been established as a resettlement area for freed slaves, with negligible European development. Convoy operations were coordinated by a naval staff aboard the elderly Union-Castle Liner Edinburgh Castle. Edinburgh Castle and a hospital ship anchored as far offshore as practicable to avoid the unhealthy conditions ashore. Tropical diseases were endemic in the oppressive heat and humidity. Local fresh water supplies were polluted. Refueling coal from the United Kingdom and oil from the West Indies was held and distributed afloat in detained merchant ships. Shore facilities were inadequate to support anti-submarine escorts for convoys until January 1941. Air cover was flown from Cornwall, Gibraltar, and Freetown when conditions allowed; but a northern Azores air gap and a southern Canaries air gap remained where U-boats and surface raiders could patrol the convoy routes unobserved. The northern gap was closed when air patrols began flying from the Azores in October 1943. Convoy SL 125 sailed on 16 October 1942 before Operation Torch discontinued sailings from Freetown. Shipping was routed along the east coast of the Americas to Halifax until convoy SL 126 sailed from Freetown on 12 March 1943. Convoy SL 128 merged with convoy MKS 12 off Gibraltar in April 1943 to be designated SL 128/MKS 12 and all subsequent SL convoys had a similar joint designation format. The effective range of U-boats was decreased by Allied capture of French Atlantic seaports in 1944. The reduced threat of submarine attack off the African Atlantic coast allowed merchant ships to sail independently to Gibraltar after convoy SL 178/MKS 69 left Freetown on 25 November 1944. ==OS convoys==