According to the testimonies provided by Major-General A.O. Mitha, it was Gul Hasan's lobbying at the Army GHQ who also saved then Brigadier Zia-ul-Haq from being terminated. Brigadier Zia who was in Jordan in 1971 was requested to be court-martial from Major-General Nawazish to President Yahya Khan for disobeying GHQ orders by commanding a Jordanian armoured division against the Palestinians, as part of actions in which thousands were killed. That event is known as "Operation Black September". It was Gul Hasan who interceded for Zia and Yahya Khan let Zia off the hook.
In 1971, he was the Chief of General Staff at the Army GHQ and allegedly either executed or approved military operations in East Pakistan. As CGS of Pakistan Army, he was heading the military operations and intelligence during this period. It is also alleged that he was the "intellectual planner" of Pakistan Army's crackdown in the East and that he preferred a military solution of the political crisis looming over the horizon of Pakistan during 1971. He lacked foresight as was viewed by some of his colleagues in Pakistan Army as "short on strategic vision but good as field commander". He, along with Air Marshal A.R. Khan, played a crucial role in forcing President Yahya Khan to step down from the presidency.
Army Commander (1971–72)
After the 1971 war which ended with unilateral surrender to India, President Zulfikar AliBhutto called Lieutenant-General Gul Hassan to take over the post of Commander in Chief of Pakistan Army, which he refused. However, he reluctantly accepted the post on several of his set conditions and took over the command of Pakistan Army. In controversy, Khan was avoided to be promoted the four-star rank as opposed to his predecessors, by Bhutto. Initially, he provided his support to President Bhutto but began obstructing the hearings of Hamoodur Rahman Commission. Reports were surfacing that Gul Hassan Khan, alongside with Air Marshal A.R. Khan, were interfering in state's affairs and influencing on Hamoodur Rahman Commission. As Army Commander-in-Chief, he lessened the role and value of the Inter–Services Intelligence which lost its importance throughout this time, and the new Army Commander did not pay any attention to ISI as he relied on Intelligence Bureau instead. The ISI's covert operations were never revealed to him and Khan was reluctant and incompetent commander to control the ISI; instead the ISI began directly reporting to President Bhutto. In 1972, the Hamoodur Rahman Commission implicated him for his role in atrocities committed in East Pakistan which eventually led towards his termination. Upon approval of his termination papers, the Governor of PunjabGhulam Mustafa Khar allegedly huddled up in a car and taken to Lahore. Khan's alleged involvement and his controversial approvals of military operations during 1971 in East Pakistan created a public resentment towards him, as he was the Director-General of the Director-general for the Military Operations. When it was cleared by Hamoodur Rahman Commission, led by Chief Justice Hamoodur Rahman, Bhutto fired Khan as Army Commander-in-Chief and appointed General Tikka Khan instead.
Family
He had three brothers and a sister. He has relatives still residing in Pabbi Nowshera District, and in Quetta, Pakistan. General Gul Hassan Khan died in 1999 and was buried in Pabbi in Nowshera District. In the last few years of his life he was dividing his time between Vienna, Austria and Rawalpindi, Pakistan. He has one son, Sher Hassan Khan, who resides in Vienna with his mother. He wrote a book Memoirs of Lt. Gen. Gul Hassan Khan.