After the Indonesian Declaration of Independence, Amir, like many his age joined the Military. He began as a Company Commander in Surabaya before being appointed Deputy Secretary of the Army Territorial Staff in the same city. He was then transferred to Yogyakarta, the center of the Indonesian National Revolution and appointed Army Staff Personnel Organizer there. It was here that he became acquainted with Suharto. Amir became close enough to Suharto that he lodged at Suharto's house with Suharto's younger brother, Probosutejo. Amir was also transferred to Suharto's Brigade.