Mogami was assigned to Rear Admiral Takatsugu Jojima's "Force B" with the carriers , and and battleship , deployed behind Vice Admiral Kurita's "Vanguard Force C". At 0530 on 19 June, Mogami launched two reconnaissance floatplanes. Later in the day, the Mobile Fleet's aircraft attacked Task Force 58 off Saipan, but suffered overwhelming losses in the "Great Marianas Turkey Shoot". At 2030 on 20 June, two hours after she was hit by torpedoes by Grumman TBM Avengers from the aircraft carrier , Hiyō exploded and sank. That night, Mogami retired with the remnants of the Japanese fleet to Okinawa, and from there to Hashirajima. Back in Kure on 25 June 1944, Mogami was refitted once again. Four triple-mount and ten single-mount Type 96 25-mm AA guns were installed, bringing the total to 60 barrels (14×3 and 18×1) and a Type 22 surface search radar and Type 13 air-search radar were fitted. On 8 July, Mogami departed Kure via Okinawa and Manila back for Singapore and Brunei, and was involved in fleet training and patrols in the Singapore-Brunei area through October. Battle of Leyte Gulf In late October, the Japanese fleet assembled in Brunei in response to the threatened American invasion of the Philippines. In the morning of 24 October 1944, Vice Admiral Nishimura ordered the launch of Mogamis floatplane to reconnoiter Leyte Gulf. The plane reported sighting four battleships, two cruisers and about 80 transports off the landing area and four destroyers and several torpedo boats near Surigao Strait. In addition, the scout reported twelve carriers and ten destroyers southeast of Leyte. The Japanese task force was attacked in the Sulu Sea by 26 aircraft from the carriers and . Mogami was damaged slightly by strafing and rockets. Battle of Surigao Strait On 25 October, between 0300-0330, the Japanese force was attacked by American PT boats and destroyers. Battleships and were hit by torpedoes. The destroyer was sunk, and the destroyer disabled, but Mogami was not hit. Fusō and Yamashiro both later sank. Between 0350–0402 hours on 25 October, after entering the Surigao Strait, Mogami was struck by four shells from the heavy cruiser , which destroyed both the bridge and the air defense center. Both the captain and executive officer were killed on the bridge, and the chief gunnery officer assumed command. While attempting to retire southward, the flagship of Admiral Shima, , collided with Mogami. Nachis bow was