At 04.58 hours on 13 Mar, 1943, U-68 attacked the convoy GAT-49 about 200 miles northwest of Curaçao, torpedoed the Cities Service Missouri and sank the Ceres 30 minutes later.

The Cities Service Missouri (Master John H.B. Morton) in station #23 was the last ship in the second column and was struck by one torpedo at the stem on the starboard side. The explosion ripped a ten foot hole in the side and vented upward, damaging the bridge and wheelhouse. The vessel stopped to determine the damage and the master thought she could be saved if they shift the ballast. At 06.10 hours a second torpedo struck the port side in the engine room and demolished the engines, just as they had brought the tanker on even keel. The U-boat surfaced about 1300 yards from the tanker and the armed guards (the ship was armed with one 5in and two .50cal guns) fired three rounds on her but all missed. By this time, water had risen to the base of the gun and 30 minutes later the master ordered the ship abandoned. All eight officers, 35 crewmen and 11 armed guards left the tanker in three lifeboats and one raft. At 07.40 hours the ship plunged stern first with her bow straight in the air. Three hours later, USS Biddle (DD 151) picked up the survivors. A boatswain drowned trying to get on the destroyer and a machinist died of wounds and burns on board. The survivors were later brought to Curaçao.