General (retd) Ehsan ul Haq was born on September 22, 1949 in Mardan. Ehsan ul-Haq graduated from PAF Public School, Sargodha in 1967, and was commissioned in Army Air Defense regiment in October 1969 in the 41st PMA Long Course. While serving in the Army, General Ehsan commanded various Infantry and Air Defense divisions. Some of Ehsan's achievements consist of graduating from Command and Staff College, Quetta, and National Defence College, Islamabad. He was promoted Brigadier in June 1992 and Major General in June 1996. After promotion, Ehsan served as the GOC of 16th Infantry Division (Pano Akil) near Sukkur, Sindh.[ He was decorated with Hilal-e-Imtiaz for his meritorious military services.

During the military coup of 1999, then Maj Gen Ehsan was Director General of Military Intelligence (DGMI), a post he continued till April 2001, when he was replaced by Major General Tariq Majid. He was then promoted as Lieutenant General and posted as the corps commander of the Peshawar Corps, a post he continued for few months till October 2001.

On May 14, 2001, Major General Ehsan was promoted to a three star general and by October 2001 was given the command of ISI. This command changeover was part of a major reshuffle that took place after the events of 9/11, and with Pakistan siding with the United States in the so called “War on Terror”. This reshuffle was also important in a sense that Lt Gen Mahmud Ahmed, the former ISI chief and a Taliban sympathizer, was prematurely retired ahead of US invasion of Afghanistan in October 2001.

After completing the 3-year term as ISI chief, in October 2004, General Ehsan was promoted to four-star general and was given the chairmanship of JCSC, replacing General Aziz Khan, who was due to retire from the Pakistan Army. General Ehsan was eighth in seniority when he ascended to the four star post, hence superseding seven senior generals. Following were the senior-most Lieutenant Generals; Hamid Javed, Javed Hassan, Munir Hafeez, Ahsan Saleem Hyat (who was promoted to four-star post of VCOAS), Tariq Waseem Ghazi, Muhammad Akram, Syed Parwez Shahid, and Ehsan ul Haq. Haq retired from military service on October 8, 2007 and was replaced by General Tariq Majid as Chairman.

General Ehsan ul Haq was later nominated as the first ever Colonel-in-Chief of the Army Air Defence (AD) on 18 December, 2004. The Colonel-in-Chief is usually the four-star general, and is the ceremonial head of his parent unit. General Ehsan was recommended to that position by General Pervez Musharraf.