At 05.02 hours on 7 Oct 1942 the unescorted Chickasaw City (Master John Walker Morton) was hit by two torpedoes from U-172, while proceeding on a non-evasive course at 10 knots with dim navigation lights burning about 85 miles south-southwest of Capetown. She was the first ship sunk by U-boats off South Africa, so the crew was not aware of the danger. The torpedoes struck the starboard side and ruptured the double bottoms and the after deck. The watch below secured the engines and the ship rapidly sank within three minutes. The ship carried ten officers, 27 crewmen, eleven armed guards (the ship was armed with one 4in, four 20mm and four .30cal guns) and one passenger. The master, seven crewmen, one armed guard and the passenger died. The survivors left the Chickasaw City in one lifeboat, two rafts and two floats. Emmermann questioned them about the ships name, port sailed from and destination and cargo carried before leaving. The 37 men were picked up after 38 hours by HMS Rockrose (K 51) (Lt E.J. Binfield, RNR) in 34°05S/17°16E and landed at Capetown the next day.

All survivors were later repatriated on the Zaandam, which was sunk by U-174 (Thilo) on 2 November. Seven crewmen and five armed guards from the Chickasaw City died.