Sadiq al-Mahdi joined the opposition and orchestrated a coup attempt in 1976, storming Khartoum with dissident forces led by Muhammad Nour Saad on 2 July.

Despite taking control initially, the rebel forces faced supply shortages and eventually succumbed to loyalist troops, ending the coup after a week.

The coup's failure led to a National Reconciliation in 1977, a brief period of pluralism and cooperation between opposition leaders and Nimeiry's government.

During that visit, King Faisal arranged a meeting between Nimeiry and Sharif Hussein al-Hindi (leader of the opposition) at the Al-Hamra Palace in Jeddah.

Sharif contacted his supporters at home and a committee led by Muhammad Hamza moved to arrange a meeting with Nimeiry, expecting the regime to change its course.

[1]Despite Sharif Hussein al-Hindi's adherence to the principles of democracy, he was convinced that the use of armed forces to overthrow the Nimeiry's government was necessary.

Sharif Hussein, who was head of the National Front, decided to move the resistance camps from the Ethiopian border to Libya with the help of Colonel Muammar Gaddafi who felt that Gaafar Nimeiry had betrayed the Arabs due to the signing of the 1972 Addis Ababa Agreement with predominantly Christian southern Sudan, ending the First Sudanese Civil War.

[1] Sadiq al-Mahdi was released from the detention centre in late 1972, and immediately fled Sudan and started watching the progress of the training operations.

[1] Sudan's General Intelligence Service knew about the plan and kept quiet about it, and began monitoring and following up the affairs of the camps in Libya.

[1][3] Two thousand followers of Sudanese opposition leader Sadiq al-Mahdi stormed Khartoum after leaving the oasis and crossing northern Darfur and Kordofan.

[4][5] The troops were commanded by Lieutenant Colonel Muhammad Nour Saad who was fired from the Sudanese Armed Forces in 1974 after being accused of plotting a coup.

[6][7] To avoid drawing attention, they arrived in Khartoum inconspicuously, disguising themselves in traditional Sudanese white robes and staying at local hotels.

[4][8] The rebel officers reportedly initiated the coup the moment Nimeiry arrived at Khartoum airport at dawn on that day coming from official visits to Washington, D.C. and Paris.

[11] Bona Malwal, Minister of Culture and Information at the time, and Abel Alier, Second Vice President of Sudan, continued to broadcast the news from Juba instead of Omdurman and painted the coup as an invasion by "mercenaries".

A limited measure of pluralism was allowed and Sadiq al Mahdi and members of the Democratic Unionist Party joined the legislature under the umbrella of the Sudanese Socialist Union.

Hassan al-Turabi, an Islamist leader who had been imprisoned and then exiled after the May Revolution, was invited back and became Justice Minister and Attorney General in 1979.

[20] Relations between Khartoum and Southern Sudan leadership worsened after the National Reconciliation due to the shift to Sharia law,[21] and adopting Arabic as the country official language.