Assigned as a convoy escort in the Battle of the Atlantic, St. Croix was torpedoed and sunk on 20 September 1943.

After the entry of the US into World War I, the United States Navy immediately required many escort ships.

[1][2] The destroyers was powered by steam provided by four White-Forster boilers to a pair of Westinghouse geared turbines.

They had storage for 400 long tons (410 t) of fuel oil, with a range of 2,500 nautical miles (4,600 km; 2,900 mi) at 20 knots (37 km/h; 23 mph).

The quarterdeck gun was later moved to the aft deck superstructure to make room for depth charge roller tracks.

[4] Following a period performing shakedown training, McCook was assigned to Destroyer Force, Atlantic Fleet.

That year, the US offered 50 "flush deck destroyers" to the UK in exchange for leases to British bases around the world.

The destroyer's final layout was three 20 mm Oerlikon cannon, one 3-inch gun, two .50 caliber machine guns, depth charge roller racks, one 21-inch torpedo tube mount sited on the deck centreline and the bridge area was revamped to make room for the new electronic equipment.

[7] The destroyer sailed for the United Kingdom on 30 November via St. John's, Newfoundland but encountered a hurricane en route and was forced to return to Canada.

HMCS St. Croix arrived at Halifax on 18 December and underwent repairs which kept the destroyer inactive until March 1941.

En route from Londonderry Port to Gibraltar on 4 March 1943 with convoy KMS 10, she assisted the corvette HMCS Shediac in the sinking of U-87 some 200 miles (320 km) off the Iberian coast.

With the addition of air escort to convoy defense in 1943, U-boat tolls in the North Atlantic diminished and many of the boats were withdrawn during the summer.

Itchen, forced to retire that evening, returned the next morning and picked up 81 survivors from St. Croix and one from Polyanthus.