Destined to play an important part in sweeping the Atlantic of German submarines, Chatelain escorted two convoys from east coast ports to Derry and Gibraltar between 20 November 1943 and 7 March 1944, and was then assigned to operate as part of the hunter-killer group formed around. During the last year of the European war, while operating with the Guadalcanal group, Chatelain joined in the sinking of two German submarines, and the capture of a third.
Sinking of the German submarine ''U-515''
Her first action took place 9 April 1944, as her group sailed from Casablanca to the United States. was detected when her radio transmissions were picked up, and planes and ships of the task group pressed home a firm attack. Chatelain forced the enemy submarine to the surface with two depth charge attacks, then joined in the general firing at point-blank range which followed, sending U-515 to the bottom at.
Capturing the German submarine ''U-505''
On 4 June 1944, Chatelain had the distinction of initiating one of the most dramatic incidents of the war, when she made a sound contact, and hurled a barrage of hedgehogs at a U-boat. A second attack by Chatelain, this time with depth charges, holed s outer hull and forced her to surface, her crew jumping overboard as she broke water. Now the task group seized its chance to carry out the boarding operation it had been planning for months, for the first capture by Americans of an intact German submarine. Successful in taking control of the submarine and executing the damage control that made its towing practicable, the group was awarded the Presidential Unit Citation for this action.
Sinking of German submarine ''U-546''
In one of the last antisubmarine actions of the Atlantic war, Chatelain took part in a 12-hour hunt for the submarine which had torpedoed on 24 April 1945. Eight other ships joined her as the group again and again attacked, sinking her finally at.
End-of-war decommissioning
Chatelain had patrol and convoy escort duty, as well as serving as plane guard during aviation exercises, until 20 November 1945, when she arrived at Charleston, South Carolina. She was decommissioned and placed in reserve at Green Cove Springs, Florida on 14 June 1946.
