After Japan capitulated on 15 August, "Barr" rendezvoused with and east of Tokyo, embarked Royal Marines from the two British warships and landed them at Yokosuka. After this mission, she proceeded to the north end of the bay to evacuate Allied prisoners of war from central Honshū. During several trips, the fast transport received on board 1,135 former POWs. After the evacuation was completed, "Barr" made one mail run to Iwo Jima between 24 and 28 September and then remained in port at Tokyo until 12 October, when she was ordered to Nagasaki for duty with the U.S. Strategic Bombing Survey. She served there as a base of operations and as a barracks ship until 1 December when she began the voyage to the United States.