After shakedown "Killen" cleared Port Angeles, Wash. on 19 August 1944, escorted a convoy from Pearl Harbor and arrived at Manus, Admiralty Islands on 14 September. Following training exercises the destroyer departed Hollandia on 12 October with the Central Philippine Attack Force that arrived off San Pedro Bay on the 20th. For the next 5 days she gave day and night fire support to troops ashore on Leyte, and during one 30-minute period on the 21st silenced three enemy artillery positions. When the Japanese Navy decided to contest the landings in the Battle of Leyte Gulf, "Killen" squadron engaged the enemy at Surigao Strait. On the morning of 25 October, at 03:25, she launched five torpedoes toward battleship "Yamashiro". One hit, slowing her to , enabled other American destroyers to maneuver for the kill. In the widespread fleet actions for Leyte, covering hundreds of thousands of nautical miles, the U.S. Fleet reduced the Japanese Fleet to an ineffective force thus greatly speeding up the advance toward Japan and end of the war.