As an army officer, Fazle Haq was commissioned in the Guides Cavalry (Frontier Force) regiment of the Armoured Corps.

During the Indo-Pakistani War of 1965, then Major Fazle Haq was part of the Guides Cavalry in the 6th Armoured Division, when the regiment launched a two-squadron attack at Phillaurah on 11 September.

By this time, General Zia-ul-Haq had imposed a martial law in the country, and Fazle Haq was concurrently appointed the Governor of Khyber-Pakhtunkhwa.

After retirement from the army in 1980, he stayed on as the governor, finally relinquishing the charge in December 1985 when the martial law was lifted in the country.

During his time as governor and corps commander, he was considered one of President Zia-ul Haq's closest confidantes and a key architect of the Afghan mujahidin groups.

He was actively involved with Afghan mujahidin groups, including Gulbuddin Hekmatyar until the end of the Soviet-Afghan war and often met with high-ranking CIA and government officials, including Attorney General of the United States William F. Smith and other political key figures for funding and support for the Afghan Jihad.

Fazle Haq was born on 10 September 1928, in Mardan (NWFP, British India), now Khyber Pakhtunkhwa, Pakistan, to an ethnic Pashtun family.