Ozawa's "Northern Force" had four aircraft carriers, two obsolete battleships partly converted to carriers, three cruisers and nine destroyers. The carriers had only 108 planes. The force was not spotted by the Allies until 16:40 on 24 October. At 20:00 Toyoda ordered all remaining Japanese forces to attack. Halsey saw an opportunity to destroy the remnants of the Japanese carrier force. The U.S. Third Fleet was formidable – nine large carriers, eight light carriers, six battleships, 17 cruisers, 63 destroyers and 1,000 planes – and completely outgunned Ozawa's force. Halsey's ships set out in pursuit of Ozawa just after midnight. U.S. commanders ignored reports that Kurita had turned back towards San Bernardino Strait. They had taken the bait set by Ozawa. On the morning of 25 October Ozawa launched 75 planes. Most were shot down by U.S. fighter patrols. By 08:00 U.S. fighters had destroyed the screen of Japanese fighters and were hitting ships. By evening, they had sunk the carriers Zuikaku, Zuihō, and Chiyoda, and a destroyer. The fourth carrier, Chitose, and a cruiser were disabled and later sank.

How many aircraft carriers were in Ozawa's "Northern Force"?