He spent two years as the head of the War History Bureau, during which time he came into contact with many important members of the Tōseiha political faction within the Army, including Kuniaki Koiso and Hideki Tōjō, and was involved in the creation of the Sakurakai organization with Kingoro Hashimoto.

His regiment was at the Battle of Lake Khasan, refusing to budge from its positions even after sustaining over 50% casualties, and then ousted the Soviet forces from a disputed hill in a night assault which the Japanese considered to be a model of its tactical type.

He had not been involved in the planning of the offensive and seriously doubted the Japanese chances for success; he had already told his staff that they might all starve to death, as Mutaguchi made no provision for logistics or resupply.

Leaving a small force to contain it, and moving by tracks to the east of Warren's brigade at Nichugard, he could, by 5 April, have struck the railway with the bulk of his division.

He considered that Mutaguchi and the HQ of Japanese Fifteenth Army were taking little notice of his situation, as they had issued several confusing and contradictory orders to him during April.

At the prompting of Lieutenant General Masakazu Kawabe, commander of Burma Area Army, doctors declared that he had suffered a mental breakdown and was unfit to stand trial on 23 November 1944.

In May 1945, he was attached to the staff of the Sendai-based Northeastern Area Army, which was assigned to defend the Tohoku region of Japan against possible Allied invasion.

For his part, Satō continued to insist until his death in 1959 that the actions he took were necessary to save the lives of his men, and that the charges of insanity made against him for withdrawing from the battle were unjustified.

Satō devoted his efforts to assisting surviving members of his former command, and he created a group of ex-army men who erected a monument to the fallen of the Imphal Campaign in Matsuyama, Ehime and in Shonai, Yamagata.