At 11.40 hours on 20 Nov 1942 the unescorted Pierce Butler (Master George Patullo Moodie) was hit by two torpedoes from U-177, while steaming on a nonevasive course at 11 knots. The torpedoes struck on the starboard side, one forward of the engine room and the other aft at the #5 hatch. Distress signals were sent, which were replied and the armed guards fired eight rounds from the forward 3in gun and seven from the 5in stern gun (the ship was also armed with four 20mm guns) in order to keep the U-boat submerged. After ten minutes the engines were secured and the eight officers, 33 crewmen and 21 armed guards abandoned ship 15 minutes after the hits in the four lifeboats. At 12.10 hours, the vessel sank by the stern. The Germans questioned the third mate and even offered to send a distress signal if none had been sent. All men were picked up about 20 hours later by HMS Fortune (H 70) (LtCdr R.D.H.S. Pankhurst, RN) and landed at Durban, South Africa.

The master George Patullo Moodie had already experienced another U-boat attack when Chilore had been torpedoed by U-576 (Heinicke) on 15 July 1942.