July 2011: After six years of autonomy and two decades of war, South Sudan formally declares independence from Sudan.

A referendum had returned a 99 per cent vote in favour of secession.

Salva Kiir becomes president; Riek Machar is his deputy. The two men have a rivalry but are also both leaders in the Sudan People’s Liberation Movement (SPLM) that led the movement to secede from Sudan.

South Sudan takes over three-quarters of the oil reserves in Sudan. Sudan retains control of pipeline and export facilities.

Other potential flashpoint issues include the location of the common border and the status of disputed regions including Abyei.

March 2012: Clashes begin and last for two months over rights to the oilfields around Heglig, a town just inside the Sudanese border. South Sudanese troops briefly occupy the area, which is responsible for half of Sudan’s crude oil production.

The two countries dispute pipeline transit costs and Sudan confiscates millions of barrels of South Sudanese crude. In January 2013 South Sudan halts its production for more than a year and accuses Khartoum of theft.

2013: South Sudan descends into a devastating civil war. Hundreds of thousands of people die, millions are forcibly displaced and parts of the country fall into famine.

July 2013: Kiir fires his deputy Machar and all government ministers, their deputies and several police brigadiers. Machar accuses Kiir of “dictatorial” behaviour.

In December Kiir claims his forces thwarted an attempted coup by Machar.

Rival army units clash in the capital Juba. The fighting spreads, fuelled by rivalries between Kiir’s majority Dinka ethnic group and Machar’s Nuer, the country’s second-largest ethnic group.

In a worsening civil war, atrocities include ethnic massacres, widespread rape and the use of child soldiers.

August 2015: Machar and Kiir sign a peace accord; Machar is reappointed vice president.

2016: Fighting between supporters of both leaders breaks out in July. Machar goes into exile, accusing Kiir of trying to have him killed.

September 2018: The former partners sign a new peace agreement to end five years of war that killed more than 380,000 and forcibly displaced four million.

A power-sharing government is slated for May 2019, with Machar again as the vice president. But the deadline is repeatedly delayed due to disputes over state boundaries, a unified national army and protection for Machar.

2020: Machar is sworn in as the first vice president in a power-sharing government. But on the ground, South Sudan remained perilously fragile. Rival forces needed to be unified in a single national army; corruption was said to be rampant, armed militias retained significant power and civilians deliberately starved, with more than half of the 12-million strong population facing food shortages.