Order of battle for Convoy SC 7
Convoy SC 7 was the seventh of the SC convoys, bound from Sydney, Nova Scotia across the North Atlantic to a number of British ports, mainly Liverpool. They were designated SC as their departure point was designated Sydney, Cape Breton in order to avoid confusion with Sydney in Australia. The convoys formed part of the battle of the Atlantic during the Second World War. Large numbers of merchants travelled together with naval escorts to protect against U-boat attacks. They were often slow, the merchants often only being capable of a speed of  around and so were particularly vulnerable to attack. This problem was exacerbated by a shortage of suitable escorts from either the Royal Canadian Navy or the Royal Navy in the early stages of the war. Convoy SC 7 left Sydney on 5 October 1940, consisting of 36 merchants initially escorted by the Canadian armed yacht and the British sloop . Having seen the convoy out of Canadian waters, "Elk" turned back on 7 October leaving the convoy to spend three quarters of the crossing escorted by the lone "Scarborough". One of the merchants, had developed engine problems and also turned back . The crossing was uneventful to begin with, the only casualty being which was straggling behind the main convoy and was torpedoed and sunk on 16 October by . The main convoy was spotted the following day by , which sank . Further sporadic attacks continued that day and the following, despite the arrival of the sloop and the corvette . The night of 18/19 October saw the successful use of the wolf pack tactics of Germany's U-boat fleet. Five U-boats; , , , and attacked en-masse, overwhelming the escorts, newly reinforced by and . They sank 16 merchants in a six-hour period, bringing  the total to twenty merchants sunk and a total tonnage lost of 79,592 Gross registered tons. The U-boats only broke off their attacks to intercept convoy HX 79 that had arrived in the area. They went on to sink a further 12 ships from this convoy, for a total of 28 ships sunk on 18/19 October, making this the deadliest two days of the battle of the Atlantic. The surviving merchants were gathered up by the remaining escorts and brought into port several days later.