On 29 Dec 1944 the Arthur Sewall (Master Harold C. Jessen) was travelling in the two column convoy TBC-21 as the fourth ship in the port column (listed as station #18), when convoy was attacked by U-322 seven miles southeast of Portland Bill Lighthouse. The two Liberty ships Arthur Sewall and Black Hawk were torpedoed and damaged beyond repair, while the U-boat was sunk by the escort shortly after the attack.

The Arthur Sewall was struck by one torpedo on the port side in the engine room. The torpedo entered the machinery space and traveled over ten feet before exploding. The blast demolished the engines and the port boilers and created a hole 20 feet long. Five men were burned badly and one officer was killed on watch below. The keel remained as the only structural member holding the ship together. The vessel settled by the stern four feet and remained on even keel. The crew of eight officers, 32 men and 29 armed guards (the ship was armed with one 5in, one 3in and eight 20mm guns) did not abandon ship. One injured fireman died next day. The tug HMS Pilot (W 03) took the vessel in tow and she arrived at Weymouth nine hours later, where she was declared a total loss.

After the war she was towed to Portland, where she was temporarily repaired before she was towed to Bremerhaven. She was loaded with obsolete chemical ammunition, towed to sea and was scuttled in the North Sea on 26 Oct 1946.