As the army was still fighting in the Philippines, its commanding officer, Lieutenant General Masaharu Homma, requested more reinforcements.

As the war situation continued to deteriorate for Japan, and Allied forces prepared to invade the Philippines, the 14th Army restructured its independent infantry brigades and reserves to form the new 100th, 102nd, 103rd, and 105th Divisions.

On October 10, 1944, General Tomoyuki Yamashita assumed the command of the 14th Area Army to defend the Philippines.

In the various battles of the Philippines campaign (1944–45) against combined American and Philippine Commonwealth armed forces in Leyte, Mindanao and parts of Luzon, the Japanese 14th Area Army suffered over 350,000 casualties, including virtually all of the 18,000 men of the 16th Infantry Division in the Battle of Leyte.

[citation needed] Troops of the 14th Area Army were responsible for the Palawan Massacre of December 14, 1944.