In Hawaii, "Barr" shuttled between Pearl Harbor and Maui, where she trained with Underwater Demolition Teams (UDTs) for night and day demolitions and shore bombardment. On 10 January 1945, "Barr" set sail for Ulithi, the main staging area for the invasion of Iwo Jima. From late January to early February, the fast transport loaded supplies, made repairs, and took part in demolition and reconnaissance training on reefs east of Ulithi. On 10 February, "Barr" and the other APDs stood out of the lagoon at Ulithi with the Iwo Jima invasion force. The transports rehearsed D-Day movements at Tinian on the 12th and 13th. Then, the advance group headed for Iwo Jima on the 14th. "Barr" arrived off the southern end of the island on 16 February; and, that afternoon, her embarked UDT 13 successfully completed its first mission. The team placed a navigational light on the hazardous Higashi Rocks despite coming under enemy fire. "Barr", however, solved the problem, silencing that gunfire with some of her own.