Born in Saga prefecture, Hyakutake graduated as an infantry officer from the 21st class of the Imperial Japanese Army Academy in 1909.

Noted generals Kanji Ishiwara and Jo Iimura were among his classmates, as was future Chinese leader Chiang Kai-shek.

After commanding the IJA 78th Infantry Regiment for one year, he took over as Superintendent of the Hiroshima Military Preparatory School in April 1936 and was promoted to major general in March 1937.

[3] He and his forces were trapped on Bougainville when the Allies established a heavily fortified perimeter at Cape Torokina, and Hyakutake was cut off from reinforcements and re-supply.

His attacks on the perimeter in December 1943 failed, and his army was forced to live off the land, hiding in jungle caves for most of the rest of the war.