South Sudan's Riek Machar is a veteran rebel who has survived years of bush warfare, assassination attempts and exile and now faces charges of treason and crimes against humanity.
Until this month, Machar was South Sudan's first vice-president under a fragile power-sharing agreement designed to stop the country slipping back into civil war.
But the perennial number two of South Sudanese politics was stripped of his place in the unity government and faces years in prison over his alleged role in an attack on government forces earlier this year.
Machar's supporters accuse the government of President Salva Kiir of cooking up the charges to sideline him and consolidate power.
Such tensions are nothing new to Machar.
Analysts say his charming gap-toothed smile and easy-going manner mask a deep capacity for anger, and involvement in some of the most horrific moments during the fight for independence from Sudan and a subsequent civil war.
Born in 1953 in the oil-producing state of Unity, Machar was the son of a chief in the Nuer community, a cattle-keeping people who are the country's second-biggest ethnic group after the Dinka.
He never underwent the traditional forehead-scarring that is a rite of passage for Nuer boys coming of age, and was sent to school instead of cattle camps, earning an engineering degree in Khartoum and a doctorate from Britain's University of Bradford.
He returned home when civil war erupted between Sudan's north and south in 1983, becoming a leader for his fellow Nuer within the rebel army, that had been dominated by Dinka forces.
- Tribe against tribe -
Machar grew frustrated with rebel commander John Garang and staged a failed 1991 coup against him and other commanders, including now-president Salva Kiir who would become his long-time rival.
As the rebel army split along ethnic lines, Machar was accused of ordering a massacre in the Dinka-dominated town of Bor in 1991, considered one of the worst atrocities of the war.
"Riek Machar is a butcher, a torturer," a Western diplomat in Juba told AFP on condition of anonymity, and he has been "a stone in South Sudan's shoe", preventing it from progressing.
The attack in Bor sparked a cycle of violence between the two ethnic groups that has persisted despite their similar culture and widespread inter-marriage.
Machar formed a breakaway rebel faction and even signed a deal with his former enemies in Khartoum for a while before rejoining the insurgents in 2002.
A peace deal was signed in 2005 that would eventually lead to South Sudan's independence in 2011, with Machar becoming vice-president under Kiir.
Their rivalry reignited in 2013 when Machar announced he would run for president in South Sudan's first election, only to find himself removed from the government by Kiir.
The dispute triggered a five-year civil war between the two, characterised by ethnic massacres reminiscent of the 1990s.
- Fragile peace -
"Dr Riek is not an angel. He has been the fundamental problem of South Sudan just like President Salva Kiir, but this is a country that has unhealed wounds in every community," said Wani Michael, a former youth leader now in exile.
After several failed peace attempts, a power-sharing agreement was forged in 2018 which saw Machar return as vice-president under Kiir.
But the relationship remained strained and the democratic transition process has failed, with elections repeatedly postponed and the leaders' respective armies never merged.
After a Nuer militia attacked an army base in Upper Nile State in March 2025, Machar was placed under house arrest and dozens of his allies arrested. Machar now faces trial on charges of treason and crimes against humanity.
Michael, the ex-youth leader, foresees more bloodshed.
"Many supporters of Riek now will go to the bush," he told AFP. "He's a political institution. He has a very big following... They will fight."
