The committee selected Henry R. Mallory and thirteen other American-flagged ships that were sufficiently fast, could carry enough fuel in their bunkers for transatlantic crossings, and, most importantly, were in port or not far at sea.

[5][6] After Henry R. Mallory discharged her last load of passengers and cargo, she was officially handed over to the Army on 24 May, one of the first three ships acquired.

[16][Note 2] Departing again from Hoboken on 14 March in the 24th convoy, Henry R. Mallory began her last journey under Army charter.

She sailed in her first convoy under Navy command on 23 April, and continued carrying troops to France, making five additional trips before the Armistice in November 1918.

On 6 July 1942, along with SS Cathcart, she rescued survivors of the British merchantmen SS Westmoreland, which had been torpedoed by German submarine U-566 220 nautical miles northward of Bermuda (unfortunately, HMS Sumar and USS Gannet (AM-41) had left Bermuda after receipt of the Westmoreland's distress signal on 2 June 1942, and, unaware of the rescue of Westmoreland's crew, fell prey to German submarine U-653 which sank USS Gannet at 0142 Hours on 8 June with the loss of sixteen lives).

[24] After first sailing to Boston and Newport, Rhode Island,[24] Henry R. Mallory departed New York as a part of Convoy SC-118 headed for Liverpool via Halifax on 24 January 1943.

[25] The crew on board Henry R. Mallory consisted of 9 officers, 68 crewmen, and 34 United States Navy Armed Guard (who manned the 11 guns on deck).

[26] It was at 06:59 on 7 February 1943 when, traveling in station 33 of the convoy, Henry R. Mallory was hit by one torpedo launched from U-402 around 600 nautical miles (1,100 km) south-southwest of Iceland.

Hit in the number three hold on the starboard side, the ship began settling by the stern and listing to port, and sank at about 07:30.

American destroyer Schenck—searching for survivors from the convoy's sunken rescue ship, SS Toward, sunk three hours earlier, also by U-402—saw lights but was denied permission to investigate.

Only when survivors were found by U.S. Coast Guard cutter Bibb some four hours later was the fate of Henry R. Mallory made clear.