The Imperial Japanese Army (IJA) was the principal ground force of the Empire of Japan. Forming one of the military branches of the Imperial Japanese Armed Forces (IJAF), it was controlled by the Imperial Japanese Army General Staff Office and the Army Ministry, both of which were nominally subordinate to the Emperor of Japan, the supreme commander of IJAF. During the 20th century, an Inspectorate General of Aviation became the third agency with oversight of the IJA. At its height, the IJA was one of the most influential factions in the politics of Japan.