With Zulfiqar Ali Bhutto facing considerable criticism and increasing unpopularity as his term progressed, democratic socialists alliance diminishing along time, claims of rigged elections  and public outcries as dissidents rose and were either imprisoned or murdered, the army felt a need to step in.

In a lightening operation led by the army chief Zia-ul-Haq, the armed forces took over Pakistan’s administration, placed the prominent figures of the Pakistan’s politics into protective custody, and dissolved the National and Provincial Assemblies, with a ban on all political activities till further notice.

With Admiral Muhammad Shariff appointed as the Chairman of the Joint Chiefs of Staff, support was pledged to Zia and the coup declared as constitutional and legal under the war-torn circumstances.

Zia after assuming power as Chief Martial Law administrator, appeared on television, and promised to hold new and neutral parliamentary elections within the next 90 days. Zia claimed that the constitution of Pakistan had not been abrogated but only suspended for a short time period.

Despite that in October 1977, Zia announced the postponement of the elections, and decided to start an accountability process for the politicians, and thus the PNA adopted a policy of “retribution first, elections later”.

During the earlier stages of his tenure as Chief martial law administrator, Zia managed to form a political wing of ISI and gained support from Bhutto’s native province by sharing power, and managed to separate the secular forces from right wing Islamists and conservatives, later purging each member of the secular front, was given a stronger hold by the Supreme Court when they introduced the Doctrine of Necessity legitimizing the coup.

But more significantly, Zia had Bhutto arrested a short time after his release where he was travelling the country amid crowds of PPP supporters. Trial proceedings against Bhutto began on 24 October 1977, on the account of Bhutto authorizing a murder of a political opponent. Bhutto was declared guilty on 8 March 1978 when the Supreme Court rules four to three in against him, and was sentenced to death. Rejecting several clemency appeals from foreign leaders, Zia upheld the death sentence, and Bhutto was hanged. The hanging of a democratically elected leader by the army was a condemned by both the international community and by lawyers and jurists across Pakistan.

Even though most of the Bhutto government had been dismissed, President Fazal Ilahi Chaudhry was persuaded to continue in office as a figurehead. After completing his term, and despite Zia's insistence to accept an extension as President, Chaudhry resigned, and Zia took the office of President of Pakistan on 16 September 1978. Thus his position was cemented as the undisputed ruler of the country. Over the next six years, Zia issued several decrees which amended the constitution and greatly expanded his power. Most significantly, the Revival of Constitution of 1973 Order granted Zia the power to dissolve the National Assembly virtually at will.

Zia during his reign as a President made several major changes to the political structure within Pakistan.

His first replacement for the parliament or National Assembly was a Majlis-e-Shoora, or "consultative council." After banning all political parties in 1979 he disbanded Parliament and at the end of 1981 set up the majlis, which was to act as a sort of board of advisors to the President and assist with the process of Islamisation. The 350 members of the Shoora were to be nominated by the President and possessed only the power to consult with him, and in reality served only to endorse decisions already taken by the government.

The 1984 referendum was a landslide victrory for Zia even though only 10 percent of the electorate voted. The referendum caused controversy as it was phrased in such a manner that voting against Zia would be a vote against Islam.

After holding the 1984 referendum, Zia succumbed to international pressure and gave permission to election commission to hold national wide general elections but without political parties in February 1985.

Before handing over the power to the new government and lifting the martial law, Zia got the new legislature to retroactively accept all of Zia's actions of the past eight years, including his coup of 1977. He also managed to get several amendments passed, most notably the Eighth Amendment, which granted "reserve powers" to the president to dissolve the Parliament.

Only of the most important decisions during Zia’s tenure was acting as an ally to USA during the afghan war. Soviet Union had interveneed in Afghanistan. Zia being ideologically opposed to the idea of communism taking over a neighbouring country, he made no secret of his intentions of monetarily and militarily aiding the Afghan resistance (the Mujahideen) with major assistance from the United States. Zia being in a position to demand billions of dollars in aid for the mujahidin from the Western states, famously dismissing a United States proposed $325 million aid package as "peanuts", and ended up obtaining a larger amount of money.

This allowed for a large influx of capital funding from USA, and as Pakistan rose in dominance on an International forum, it allowed Pakistan to gain a firm footing globally with the country experiencing an average annual growth in the GNP of 6.8%—the highest in the world at that time.

One of the earliest initiatives taken by Zia in 1977, was to militarise the integrated atomic energy programme which was founded by Zulfikar Ali Bhutto in 1972. This atomic bomb project had no boundaries with Munir Ahmad Khan and Dr. Abdul Qadeer Khan leading their efforts separately and reported to Bhutto and his science adviser Dr. Hassan who had little interest in the atomic bomb project. The PAEC conducted the cold-fission test of a fission device, codename Kirana-I on 11 March 1983 at the Weapon-Testing Laboratories-I, under the leadership of weapon-testing laboratory's director Dr. Ishfaq Ahmad.

Zia was a strong supporter of a truly Islamic Pakistan and the centre piece of his policy was Shariatisation or Islamisation. The drinking and selling of wine by Muslims, along with nightclubs, and horse racing was banned by Prime Minister Bhutto in an effort to stem the tide of street Islamization. Zia established "Sharia Benches" in each High Court, and bolstered the influence of ulama. The Hudood Ordinance added new criminal offences of adultery and fornication to Pakistani law, and new punishments of whipping, amputation, and stoning to death. He also introduced an interest-free banking system.

Zia used unorthodox methods to ensure peace as a means of diplomacy. With Indian and Pakistani troops still massed in a tense border confrontation, Zia left for India to watch an India-Pakistan cricket match. Zia told Pakistani journalists that the two leaders had expressed their satisfaction at an easing of their conflict. He said he had repeated a previous invitation for Gandhi to visit Pakistan, something the Indian leader has been reluctant to commit himself to do.

Zia’s death on 17th August, 1988 was a controversial matter. On board the C-130 were a total of 31 people, including the then President of Pakistan General Muhammad Zia-ul-Haq, the United States Ambassador to Pakistan, Arnold Raphel, General Herbert M. Wassom, the chief of the U.S. military mission in Pakistan, and a group of senior officers from Pakistan army. A few minutes after take off the tower lost contact with Zia’s plane and the plane plunged from the sky with such force that it exploded to pieces, killing all on board. The crash still remains a source of skepticism today where books such as ‘A Case of Exploding Mangoes’ are written about it.