The Japanese 16th Area Army was formed on February 1, 1945 under the General Defense Command as part of the last desperate defense effort by the Empire of Japan to deter possible landings of Allied forces in Kyūshū during Operation Downfall (or Operation Ketsugō (決号作戦, Ketsugō sakusen) in Japanese terminology).

The Japanese 16th Area Army was headquartered in what is now part of Chikushino city, Fukuoka Prefecture.

By the time of the Japanese surrender, the 16th Area Army had 916,828 personnel on Kyushu either in position or in various stages of deployment.

[3] The Japanese did not formally decide to stake everything on the outcome of the Battle of Kyūshū, but they concentrated their assets to such a degree that there would be little left in reserve.

Weapons, training, and uniforms were generally lacking: some men were armed with nothing better than muzzle-loading muskets, longbows, or bamboo spears; nevertheless, they were expected to make do with what they had.