As western Atlantic coastal convoys brought an end to the "Second Happy Time", Admiral Karl Dönitz, the Befehlshaber der U-Boote (BdU) or commander in chief of U-Boats, shifted focus to the mid-Atlantic to avoid aircraft patrols.

[4] B-Dienst decrypted message traffic detailing routing and composition of convoy SC 107, and fifteen U-boats of wolfpack Veilchen (violet) were deployed to intercept it.

[1] At sunset Flower-class corvette HMS Celandine was sent to investigate the closest HF/DF fix eight miles off the port quarter; and Restigouche made a sweep astern.

When corvette HMCS Arvida had a radar malfunction, U-402 went undetected as it penetrated the starboard side on the convoy screen about midnight to torpedo the British freighter Empire Sunrise.

Harbor tugs USS Uncas and Pessacus had been attached to the convoy for passage to Iceland, and were detailed to act as rescue ships because Stockport was carrying three times her intended capacity.

U-89 torpedoed the convoy commodore's freighter Jeypore after sunset on 3 November; but snowflake illumination was minimal because most ships had exhausted their supply of pyrotechnics during the earlier attacks.

[7] The entire convoy and nearby U-boats were shaken thirty minutes later by a heavy explosion believed to have been one of the largest prior to atomic bomb testing.

The magnitude of the explosion temporarily stopped the engine of the rescue tug six miles astern of the convoy and caused several ships to believe they had been torpedoed.

[7] U-89 torpedoed the British freighter Daleby shortly before the convoy escort was reinforced by the United States Coast Guard Treasury-class cutter Ingham and the Wickes-class destroyers Leary and Schenck from Iceland.