The SC convoys were a series of North Atlantic convoys that ran during the battle of the Atlantic during World War II.
They were east-bound slow convoys originating in Sydney, Nova Scotia, Canada (designated as Sydney, Cape Breton by the Allied navies to avoid confusion with Sydney, New South Wales); from there they sailed to ports in the UK, mainly Liverpool. The Royal Canadian Navy base responsible for the Sydney operations was HMCS Protector. The first convoy, SC-1, departed Sydney Harbour on 15 August 1940.
For a time after the entry of the United States into the war the point of origin was switched to New York, but congestion problems there resulted in a further move, this time to Halifax, Nova Scotia. However, the SC designation was retained throughout.
SC convoys ran from August 1940 until May 1945, although they were suspended during the summer of 1944 when a number of escort groups were diverted to cover the Normandy landings. During this period all east-bound traffic sailed in the HX series, which ran as Fast or Slow convoys, and whose sizes were effectively doubled.
A total of 177 SC convoys ran during the campaign, totalling 6,806 ships. Only 3 failed to complete the passage: SC 52 suffered an attack shortly after leaving port, and was forced to return; and SC 62 and SC 63 were both scattered by appalling weather conditions which forced those ships to proceed independently.
Of these formations, 29 (around 20%) were attacked; they saw the loss of 145 ships ( though this number does not include stragglers, perhaps the same number again) and a further 18 lost in marine accidents (perhaps 340 in total; around 5%).