In March 1939, he was appointed commander of the Utsunomiya Regimental District, a recruiting and training unit responsible for raising troops in Tochigi Prefecture.

Okabe was assigned command of then IJA 13th Infantry Regiment in October 1940, and was promoted to major general in August 1941.

He led the regiment at the Battle of Changsha from September 18 to October 6, 1941 including after his promotion to commander of the IJA 51st Infantry Group.

In May 1943, he was rotated back to Japan and attached to the Eastern District Army, which was responsible for defense of Tokyo and its environs.

In March 1945, he was made commander of the IJA 79th Independent Mixed Brigade, which was sent to Andong in southern Manchukuo, where he remained until the surrender of Japan.