In March 1987, Prime Minister Mohammad Junejo announced in the news media of appointing Lieutenant-General Beg as a Vice-Chief of Army Staff, promoting him as the four-star rank general in the army.

Though, General Beg did not supersede anyone and was the most senior, the promotion was notable due to the opposition shown by President Zia-ul-Haq who wanted Lieutenant-General Zahid Ali Akbar, an engineer, as vice army chief.

Despite his four-star command assignment, General Beg had to report his duties and decisions to President Zia who had been army chief since 1976.
Eventually, General Beg succeeded President Zia as the new army chief and the command of the army when the latter died in an accidental plane crash on 17 August 1988.
American military authors regarded Beg as "mild but bookish general" keen to drive the country towards the tracks of democracy.

The United States military regarded Beg as "Unpredictable General" could not be counted on to continue close military cooperation with the United States as Zia did in the 1980s.
The Pentagon had commented on Beg as "a professional soldier" with no political ambitions, but independent-minded and unpredictable.
In 1988, one Pentagon military official added that "Beg is hard to figure out and difficult to read his mindset unlike other Pakistan army generals, he hasn't been particularly friendly with the US."

Against the popular perception to take over, Beg endorsed Ghulam Ishaq Khan as President and ultimately called for new general elections which resulted in a peaceful democratic transfer of government to the Pakistan Peoples Party (PPP) with Benazir Bhutto as the Prime minister.
Beg did not consult any of his corps commanders or principal staff officers (PSOs) and called on the Chief of Naval Staff, Admiral Iftikhar Sirohey, and Chief of Air Staff Air Chief Marshal Hakimullah, to discuss the matter briefly and within three hours of General Ziaul Haq's death, restored the Constitution and handed over power to Ghulam Ishaq Khan.
It was an unprecedented decision in favour of democracy and the rule of law.

Mirza Aslam Beg was endorsed by Prime Minister Benazir Bhutto who confirmed his four-star appointment as chief of army staff until 1991, when he was replaced by General Asif Nawaz.
Unlike General Zia, Beg initiated a massive re-evaluation and education training program for the inter-services officers.
In 1988, Beg's personal initiatives led to sending of hundreds of inter-services officers to Western universities for advanced degrees.
By 1991, several of the inter-services officers had gained post-graduate degree in operational and technical training.

In 1988, Prime Minister Benazir Bhutto conferred Beg with specially designated civil award for Mirza Aslam Beg for restoring the democracy, Tamgha-e-Jamhuriat (lit.
Medal of Democracy).
In fact, Beg is the only in Pakistan, and yet the only four-star army general to have been decorated with such honor.
Although Prime Minister Benazir Bhutto was criticized for decorating a four-star general with a civilian award, she used to justify her decision, saying that Beg deserved this honour because he refrained from indulging in yet another military adventure like Zia and instead helped Pakistan to a peaceful transition of power through general elections.

On 16 August 1991, General Beg retired from his military serving, completing 41 years of service, and handing over the command to General Asif Nawaz.
As an army chief, General Beg is credited by an Australian Army expert for encouraging "wider thinking about tactics" within the Pakistan Army, particularly for establishing a much improved logistics chain and "contributed immensely to the army’s warfighting capabilities."
In March 1987, Prime Minister Mohammad Junejo announced in the news media of appointing Lieutenant-General Beg as a Vice-Chief of Army Staff, promoting him as the four-star rank general in the army.
Though, General Beg did not supersede anyone and was the most senior, the promotion was notable due to the opposition shown by President Zia-ul-Haq who wanted Lieutenant-General Zahid Ali Akbar, an engineer, as vice army chief.
Despite his four-star command assignment, General Beg had to report his duties and decisions to President Zia who had been army chief since 1976. Eventually, General Beg succeeded President Zia as the new army chief and the command of the army when the latter died in an accidental plane crash on 17 August 1988. American military authors regarded Beg as "mild but bookish general" keen to drive the country towards the tracks of democracy.
The United States military regarded Beg as "Unpredictable General" could not be counted on to continue close military cooperation with the United States as Zia did in the 1980s. The Pentagon had commented on Beg as "a professional soldier" with no political ambitions, but independent-minded and unpredictable. In 1988, one Pentagon military official added that "Beg is hard to figure out and difficult to read his mindset unlike other Pakistan army generals, he hasn't been particularly friendly with the US."
Against the popular perception to take over, Beg endorsed Ghulam Ishaq Khan as President and ultimately called for new general elections which resulted in a peaceful democratic transfer of government to the Pakistan Peoples Party (PPP) with Benazir Bhutto as the Prime minister. Beg did not consult any of his corps commanders or principal staff officers (PSOs) and called on the Chief of Naval Staff, Admiral Iftikhar Sirohey, and Chief of Air Staff Air Chief Marshal Hakimullah, to discuss the matter briefly and within three hours of General Ziaul Haq's death, restored the Constitution and handed over power to Ghulam Ishaq Khan. It was an unprecedented decision in favour of democracy and the rule of law.
Mirza Aslam Beg was endorsed by Prime Minister Benazir Bhutto who confirmed his four-star appointment as chief of army staff until 1991, when he was replaced by General Asif Nawaz. Unlike General Zia, Beg initiated a massive re-evaluation and education training program for the inter-services officers. In 1988, Beg's personal initiatives led to sending of hundreds of inter-services officers to Western universities for advanced degrees. By 1991, several of the inter-services officers had gained post-graduate degree in operational and technical training.
In 1988, Prime Minister Benazir Bhutto conferred Beg with specially designated civil award for Mirza Aslam Beg for restoring the democracy, Tamgha-e-Jamhuriat (lit. Medal of Democracy). In fact, Beg is the only in Pakistan, and yet the only four-star army general to have been decorated with such honor. Although Prime Minister Benazir Bhutto was criticized for decorating a four-star general with a civilian award, she used to justify her decision, saying that Beg deserved this honour because he refrained from indulging in yet another military adventure like Zia and instead helped Pakistan to a peaceful transition of power through general elections.
On 16 August 1991, General Beg retired from his military serving, completing 41 years of service, and handing over the command to General Asif Nawaz. As an army chief, General Beg is credited by an Australian Army expert for encouraging "wider thinking about tactics" within the Pakistan Army, particularly for establishing a much improved logistics chain and "contributed immensely to the army’s warfighting capabilities."
Mirza Aslam Beg