Aziz graduated from the Pakistan Military Academy in April 1971 as the Battalion Senior Under Officer and received the Sword of Honour as well as the Presidents Gold Medal for his performance. He was commissioned in the 10 Battalion of the Baloch Regiment with which he actively participated in the 1971 India-Pakistan War and later on also commanded. He attended the Company Commander Course at Fort Benning, Georgia (USA) and the Command and General Staff Course at Fort Leavenworth, Kansas (USA). Aziz is also a graduate of the National Defence University, Pakistan. His military career has placed him in pivotal posts during critical periods in Pakistan. He served as the General Officer Commanding of the 12th Infantry Division stationed at Murree. During the Kargil conflict of 1999, he served as DG of the Inter-Services Intelligence (ISI) Agencies' Analysis Wing. That same year, he was appointed to the role of Director General Military Operations where he played a crucial role in the October 1999 Pakistani coup d'état that brought Pervez Musharraf to power. After the events of the September 11 attacks in 2001, he was serving as General Officer Commanding 12 Division when the United States invaded Afghanistan. Later that year he was appointed as Chief of General Staff at GHQ. He finally retired from the army in 2005 after having held the post of Lahore Corps Commander for two years during which time he also launched a massive inquiry against corruption in the Defence Housing Authority, Lahore.