SL convoys

SL convoys were a numbered series of North Atlantic trade convoys during the Second World War. Merchant ships carrying commodities bound to the British Isles from South America, Africa, and the Indian Ocean traveled independently to Freetown, Sierra Leone to be convoyed for the last leg of their voyage to Liverpool.

On the basis of 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 sailed 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 Freeport; 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.

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