At 07.14 hours on 23 Feb, 1943, U-628 (Hasenschar) fired a spread of two FAT torpedoes at the convoy ON-166 in grid BD 4564. One torpedo damaged Winkler, which was later sunk by U-223 (Wächter) and the other hit the Glittre, which was later sunk by U-603 (Bertelsmann).

The Winkler (Master Arthur Gasso) had been in station #63, but fell behind because one of the four diesel engines broke down in rough weather at 02.10 hours. About five hours later, one torpedo struck on the port side between #2 and #3 tanks and caused a list to port. At 07.45 hours, an U-boat was spotted ahead in about 500 yards distance, immediately the forward gun fired five shells and claimed a possible hit on the conning tower before it dived. Shortly afterwards the lifeboats from Glittre were spotted and the master offered to pick them up but they refused because at 09.30 hours HMS Dianthus (K 95) arrived on the scene, ordered the tanker to return to the convoy on a zigzag course and followed after picking up the survivors.

At 09.51 hours, U-223 fired a spread of three torpedoes at Winkler and hit her with two torpedoes in the port quarter, blowing out the bottom and causing the ship to sink within 45 seconds. The master, 32 crew members and 18 armed guards were forced to jump overboard because they had no time to launch any lifeboat or raft. 14 crew members and five armed guards were lost. The corvette was not able to attack the U-boat because it dove underneath the survivors, so they picked up the survivors until 10.55 hours, then returned to the convoy and landed them at St.Johns on 26 February.