Sudan had been independent for just over thirteen years when Colonel Gaafar Nimeiry's tanks rolled through the Khartoum-Bahri-Omdurman triangle. In that short span, the country had already cycled through enough governments to exhaust most constitutions. Ismail al-Azhari of the National Unionist Party became prime minister at independence on 1 January 1956, only to be replaced by Abdallah Khalil of the Umma Party six months later via a vote of censure. Lt. General Ibrahim Abboud then carried out a military self-coup in November 1958, suspending the constitution. Abboud resigned after popular protests in November 1964. A brief democratic period followed, with Muhammad Ahmad Mahgoub forming a coalition government in June 1968. For ordinary Sudanese, the rotation had become familiar: new men in Khartoum every few years, sometimes through elections, sometimes not.

By 4 am on 25 May, key installations in the capital triangle had been occupied. Sudanese Army generals were under arrest. At 7 am, Radio Omdurman broadcast recorded speeches by Nimeiry and Babiker Awadalla, setting out the new government's plans. Later that morning came the names of the new Council of Ministers - a composition agreed upon two days earlier between Awadalla and six key officers. The speed was characteristic of successful African coups of the period. You listened to the radio. You heard who was in charge now. You adjusted. In Khartoum's coffee houses and along the Nile corniche, the conversations were tentative: was this another rotation, or something that would last?

Nimeiry's government pursued what it called a radical Arab nationalist and leftist program. Widespread nationalization of private property followed. The new regime also made its most consequential gesture toward the south: on 9 June 1969, barely two weeks after the coup, it declared regional autonomy for southern Sudan. The First Sudanese Civil War had been grinding for nearly fourteen years by then, and the offer of amnesty and autonomy was a real attempt to end it. The eventual Addis Ababa Agreement of 1972 would make the offer concrete. The peace would last, remarkably, until Nimeiry himself destroyed it in 1983 by imposing Sharia on the non-Muslim south - an act that restarted the war that would eventually birth South Sudan.

The Revolutionary Command Council's composition had been planned in advance, but expanded during the course of 25 May. While his fellow Free Officers secured key army units, Nimeiry quietly met with two officers who had voted against the coup at the Free Officers' April meeting: Lt. Col. Babikir al-Nur and Maj. Abu al-Qasim Hashim. Al-Nur was the highest-ranking officer associated with the Sudanese Communist Party. Hashim had deep civilian links to Arab nationalists and Nasserists. Nimeiry, without consulting his fellow plotters, brought both men in. Another communist-affiliated officer, Hashem al-Atta, joined too. The resulting council was not just the coup-makers but a deliberately broadened coalition - a political calculation that would come undone violently only two years later, in the 1971 attempted counter-coup and its bloody aftermath.

From altitude, Khartoum reveals itself at the hinge where the Blue Nile meets the White Nile - the Mogren, as Sudanese call the confluence. The three cities that make up the metropolitan area - Khartoum proper, Khartoum Bahri (North), and Omdurman on the west bank - form the arms of a Y-shape visible from 30,000 feet. The presidential palace, where so many of Sudan's power transfers have played out, sits on the east bank of the Blue Nile in central Khartoum. Omdurman, the largest of the three cities, was the Mahdist capital in the 19th century before the British conquered it. Radio Omdurman - the station through which so many coups have been announced to Sudanese listeners - still broadcasts from here.