Callaghan sailed from the West Coast 5 February 1944 to join the 5th Fleet in defending against air raids on the Palaus, Yap, Ulithi, and Woleai from 30 March to 1 April.

Based on Manus in April, Callaghan supported the Hollandia operation as picket ship during air strikes and screening the valuable tankers.

At Saipan, Callaghan's guns joined in driving off a heavy Japanese air attack on 17 June, helping shoot down three enemy aircraft.

With the invasion of the Philippines scheduled for mid-October 1944, Callaghan steamed in the screen of the carrier force conducting essential preliminary neutralization of Japanese airfields in Formosa and Okinawa.

This initiated prolonged fire support and screening duty in the dangerous waters off Okinawa during which, in addition to invaluable aid to the troops, Callaghan joined in the sinking of a Japanese midget submarine and shot down three dive bombers.