Convoy ON 166
Convoy ON 166 was the 166th of the numbered ON series of merchant ship convoys Outbound from the British Isles to North America. Sixty-three ships departed Liverpool 11 February 1943 and were met the following day by Mid-Ocean Escort Force Group A-3 consisting of the s and and the s,,, and. The convoy suffered losses before arriving at New York City, US.
Background
As western Atlantic coastal convoys brought an end to the Germans' "second happy time", Admiral Karl Dönitz, the Befehlshaber der U-Boote or commander in chief of U-Boats, shifted focus to the mid-Atlantic to avoid aircraft patrols. Although convoy routing was less predictable in the mid-ocean, Dönitz anticipated that the increased numbers of U-boats being produced would be able to effectively search for convoys with the advantage of intelligence gained through B-Dienst decryption of British Naval Cypher Number 3. However, only 20 percent of the 180 trans-Atlantic convoys sailing from the end of July 1942 until the end of April 1943 lost ships to U-boat attack.21 February
On 20 February sighted the convoy scattered by sailing eight days in a northwesterly gale. torpedoed the straggling Norwegian Stigstad on the morning of 21 February. was sunk by a No. 120 Squadron RAF B-24 Liberator that afternoon, and Campbell sank a U-boat that evening. Postwar analysis concluded that Campbell sank, but later re-evaluation indicated that the attack may have destroyed.torpedoed the British Empire Trader at 2032 and the Norwegian NT Nielsen Alonso at 0153 on the night of February 21–22. Both ships were hit by a single torpedo on the port side, flooding the forward hold, and boiler room, respectively. from the following convoy ONS 167 was ordered to reinforce the convoy escort.