South Sudan's Riek Machar profiled
Once married to a British aid worker, Riek Machar has been a central figure in Sudanese and South Sudanese politics for around three decades.
After more than two years of civil war, he has now returned to the capital, Juba, to take the post in a new unity government.
Mr Machar is reputed to be a wily operator, switching sides on several occasions during the north-south conflict as he sought to strengthen his own position and that of his Nuer ethnic group in the murky political waters of South Sudan.
Born in 1953, he married Emma McCune in 1991 who died two years later, while pregnant, in a car accident in the Kenyan capital, Nairobi.
She was dubbed by some in the media as the "warlord's wife", a reference to Mr Machar's role as a leading commander in the armed wing of the Sudan People's Liberation Movement (SPLM), which was then spearheading the war for South Sudan's independence from the north.
After a peace deal was signed in 2005 to herald the end of that conflict and the sudden death of its leader John Garang, the SPLM appointed Mr Machar as the vice-president of the regional South Sudanese government.
In a sign of the enormous influence he wielded, Mr Machar retained the post after South Sudan became independent in 2011 until his dismissal in 2013.
Later that year, President Salva Kiir accused him of plotting a coup, which prompted him to flee the capital, Juba.
He denied the allegation, but it triggered a civil war which killed tens of thousands of people and left some two million homeless.
After protracted negotiations by regional mediators, Mr Machar has been sworn in again as vice-president and says he aims to help rebuild the world's youngest country that has been devastated by the conflict.
Coming from South Sudan's second largest ethnic group, the gap-toothed Mr Machar's presence in the upper echelons of power was seen as vital to promote ethnic unity with the Dinka majority.
Recalling meeting him in 2005, BBC Africa's David Amanor said he had a commanding physique.
"He's got a steely but also gentle look. He's well-spoken and well-educated," he said.
At the time, Mr Machar had swapped his military fatigue for an English suit, playing the role of a mediator between the Ugandan government and the Lord's Resistance Army (LRA) rebel movement.
He saw the LRA as a major threat, believing that it could destabilise South Sudan, where it had military camps.
Although the peace initiative failed, Mr Machar - now married to South Sudanese politician Angelina Teny - was impressive as a mediator.
"He showed immense patience - the skills of a diplomat," recalled Mr Amanor, who covered the talks.
'Prophet of doom'
But critics say he also showed his ruthless side when he backed government forces in their fight against prominent South Sudan rebel leader George Athor, who was accused of waging a new "proxy war" on behalf of the Khartoum government, which it denied.
In December 2011 - some five months after independence - Mr Machar announced that Mr Athor had been killed near the Sudan-South Sudan border.
Riek Machar: At a glance
- Studied at UK's University of Bradford, obtaining a PhD in philosophy and strategic planning in 1984
- Married UK aid worker Emma McCune in 1991; she died while pregnant
- Switched sides on several occasions during the north-south conflict as he sought to strengthen his position and that of his Nuer ethnic group
- Sacked as South Sudan's vice-president in July 2013
- Denied he was plotting a coup in December 2013 - but his fallout with President Kiir led to more than two-years of conflict
- Sworn in again as vice-president in April 2016 as part of an internationally brokered peace deal
For his SPLM critics, Mr Machar was becoming too powerful when President Kiir sacked him from the government.
Mr Kiir labelled him as a "prophet of doom", continuing his actions of the past - an apparent reference to the fact that he had challenged the authority of Mr Garang, the SPLM's founding leader, in the early 1990s.
Despite high-profile mediation efforts by then-Kenyan President Daniel arap Moi and US congressmen, Mr Machar refused to sign a peace declaration with Mr Garang, who was lionised by SPLM fighters at the time.
This was seen as a major blow to efforts by many African and Western governments to present a united front against the Islamist-led government of Sudan's President Omar al-Bashir.
By then leading a breakaway rebel group, Mr Machar signed a peace accord with Mr Bashir's government in 1997.
It gave him his first taste of state power, with his appointment as an assistant to President Bashir, but he quit not long afterwards re-launching a rebellion.
However, Mr Garang's SPLM remained deeply suspicious of him, accusing him of receiving covert support from the Khartoum government - a charge he denied.
In 2002, he finally buried the hatchet with Mr Garang, rejoining the SPLM.
Now, he has returned to the centre of power, possibly calculating his next move to achieve his long-held ambition of becoming president.
It is a far cry from the days when he was a student in the UK, obtaining a PhD in philosophy and strategic planning from the University of Bradford in the mid-1980s.
It was also a time of political revolt in his homeland with the SPLM having just been formed to campaign against northern rule.
Mr Machar chose to join the fight - and has never looked back.