Convoy ONS 5 - Background

Background

ONS 5 consisted of 43 ships bound from Liverpool to Halifax. The ships were either in ballast or carrying trade and export goods. The convoy departed Liverpool on 21 April 1943, and would arrive in Halifax three weeks later on 12 May. It was under the command of JK Brook RNR as Convoy Commodore, traveling in the Norwegian freighter Rena. The escort was provided by Mid-Ocean Escort Force group B7, 7 warships under Captain Peter Gretton, in the destroyer Duncan. Also in the group were the destroyer Vidette, frigate Tay, and corvettes Sunflower, Snowflake, Loosestrife, and Pink. The group also contained 2 trawlers, Northern Gem and Northern Spray as rescue ships, and the fleet oiler British Lady for mid-ocean re-fuelling. The convoy was joined by other escort vessels as the battle progressed.

ONS 5 was just one of the allied convoys at sea at the end of April; also in the Western Approaches were ON 180, just leaving, and HX 234, just arriving. Approaching the Americas were ONS 4 and ON 179; departing was SC 128, while in mid-Atlantic, due to pass ONS 5 east of Greenland, was SC 127. Two other east-bound convoys, HX 235 and HX 236, were also in mid-Atlantic, following a southerly route. This accounted for over 350 ships on the move in the north Atlantic at that time.

Ranged against them were 58 U-boats in 3 patrol lines; Specht (Woodpecker) with 17 boats south of Greenland on the western side of the Air Gap; Meise (Bluetit) with 30 boats east of Greenland covering the northern route, and Amsel (Blackbird) with 11 boats, south of Meise covering the southern route.

Meise had been deployed to catch SC 127, which had been identified by B-Deinst, but on 26 April SC 127 had slipped through a gap in the line and escaped undetected. Realizing what had happened on 27 April,, and aware that a slow west-bound convoy was imminent, Meise was re-configured; the easternmost boats (16 in all) formed the patrol line Star (Starling) to intercept it. At 8am on 28 April U-650 sighted ONS 5, and group Star quickly gathered for the attack.