At 07.27 hours on 9 Oct 1943 the Yorkmar (Master William Augustus DePuey) in station #111 of convoy SC-143 was hit by one torpedo from U-645 about 475 miles south of Iceland. The torpedo struck on the starboard side between the #4 and #5 holds and blew off both hatch covers, brought down the main mast and caused the ship to settle fast by the stern. The engines were secured and the eight officers, 31 crewmen and 28 armed guards (the ship was armed with one 4in, one 3in and eight 20mm guns) abandoned ship in a great confusion because they not evenly distributed themselves on the three intact lifeboats (one had been lost earlier in heavy seas). One boat was launched with two occupants only, another overcrowded boat swamped in the rough seas and a third was not launched. Other survivors jumped overboard and swam to two rafts. The ship sank by the stern after 15 minutes on even keel after having listed 35° to starboard. One officer, ten crewmen and two armed guards drowned. The survivors were picked up within two hours by HMCS Kamloops (K 176) and HMS Duckworth (K 351) and landed at Londonderry and Belfast on 9 and 11 October.