At 09.32 hours on 20 Sep 1943, U-238 fired four torpedoes at convoy ON-202 about 500 miles southwest of Iceland and reported two hits on the ships in station #11 and #21. The Frederick Douglass in station #11 was damaged and the Theodore Dwight Weld in station #21 was sunk.

The Theodore Dwight Weld (Master Michael Fromanack) was hit on the port side in the settling tanks opposite the #3 hold. Only a few seconds later the boilers blew up and broke the ship in two just forward of the bridge. The stern sank almost immediately so that the master, seven officers, 34 crewmen and 28 armed guards (the ship was armed with one 3in and nine 20mm guns) on board had no time to launch any lifeboats or rafts. The most survivors were washed off the stern or jumped overboard from the bow and clung to three doughnut rafts that floated free until they were picked up by the British rescue ship Rathlin, one armed guard was taken off the bow section by its motor rescue boat. Two officers, 21 crewmen and 15 armed guards were rescued by the rescue ship and landed in Halifax on 28 September, but one crewman died onboard and was buried at sea.