Promoted to major general on 1 August 1929, he was assigned to command the 39th Brigade of the IJA 20th Division, stationed in Korea.

In early 1937, he briefly commanded the Imperial Guards Division, before being transferred to China at the beginning of the Second Sino-Japanese War.

After the Marco Polo Bridge Incident Nishio was sent to North China, and took command of the Second Army on 26 August 1937.

Shortly after the defeat his army suffered in the Battle of Taierzhuang, he was replaced and returned to Tokyo to be Inspector-General of Military Training.

His force withstood the Chinese 1939-40 Winter Offensive and rolled back their gains in the spring with many operations including the Battle of Zaoyang-Yichang.