Hemedti’s fighting skills were honed when his loyalists and other irregulars allied with Sudan’s government to help quash a rebellion in Darfur that had erupted in 2003.
Burhan now in his early 60s, has proved a deft political operator after rising under Bashir before also dumping him.
For now, the battle for Khartoum rages on amid fierce fighting for control of strategic assets.
A battle that is hammering Khartoum and dragging Sudan to the brink of civil war pits the country’s army chief and his regular forces against the streetwise fighters loyal to a former warlord.
Army head General Abdel Fattah al-Burhan controls heavy weapons and the air force, but his soldiers face an irregular force led by the wealthy one-time militia leader General Mohamed Hamdan Dagalo, better known as ‘Hemedti’.
Hemedti's Rapid Support Forces (RSF), which analysts say may have 100,000 or more paramilitary fighters, have already proved a tricky opponent, evacuating bases in the capital that have come under attack and melting away into residential areas where heavy armour and conventional military tactics lose any advantage.
With their once uneasy alliance in tatters, the two men are battling to make a killer blow in a power struggle that may instead deliver protracted conflict and more instability shredding prospects for peace and economic revival in Sudan after decades of autocracy, military rule and international isolation.
Fighting that erupted on Saturday has already killed at least 270 people, injured 2,600, forced dozens of hospitals to close and left residents cowering at home with dwindling supplies.
Hemedti, a school dropout now in his late 40s, began as a camel trader in Darfur. According to his former assistant Muhammad Saad, he first took up arms after men attacked his trade convoy killing about 60 people from his extended family and stealing his livestock.
His fighting skills were honed when his loyalists and other irregulars allied with Sudan’s government to help quash a rebellion in Darfur that had erupted in 2003. The militia forces became known as the Janjaweed, a term loosely derived from the Arabic for 'devils on horseback' that reflected a fearsome reputation.
The International Criminal Court (ICC) accused former Sudanese president Omar al-Bashir of masterminding genocide, crimes against humanity and war crimes in the campaign he launched to crush the revolt.
Bashir and his government denied allegations of atrocities saying only rebels were targeted in the conflict that lasted years, killed about 300,000 people and displaced 2 million.
Amid the bloodshed, Hemedti captured the attention of Bashir, a general who came to power in a 1989 coup. Hemedti's militia which morphed into the RSF, became a government enforcer. Bashir also gave his family and associates free rein to sell Sudan's gold, helping him amass a fortune.
Hemedti would later turn on his benefactor when Bashir was ousted in 2019. In the aftermath, Hemedti secured the post of deputy head of state, a position that technically reports to Burhan. He also transformed himself into a politician, giving speeches, meeting Western diplomats and winning backers abroad.
Like Sudan's army, the RSF deployed fighters to Yemen where Gulf Arab states have fought a proxy war for years against Iranian-backed Houthis.
"Hemedti planned on becoming the number one man in Sudan. He has unlimited ambition," an anonymous opposition figure previously said of him.
His RSF may lack typical army discipline, but they are skilled fighters with their AK-47 assault rifles and rocket-propelled grenades and their trademark pick-up trucks with mounted machine guns making them a highly agile force.
They have also retained a brutal reputation. Protesters blamed the RSF for a bloody crackdown on a protest camp in 2019 in Khartoum outside Sudan’s Defence Ministry after Bashir's ousting. More than 100 people were killed. Hemedti denied any role.
Hemedti's rival cuts a very different figure. Burhan is a career soldier with 41 years of service mostly under Bashir, whose rule saw Sudan become an international pariah that was on the US terrorism list while its economy was battered by sanctions.
Burhan, de facto leader
Burhan now in his early 60s, has proved a deft political operator after rising under Bashir before also dumping him. He said he was among the military figures who told Bashir to step down.
Since then, he has become Sudan's de facto leader and entered a power-sharing deal with civilians that was meant to put Sudan on a three-year path to democracy.
"What the country is going through now is a real threat and danger to the dreams of the youth and the hopes of the nation," Burhan said after seizing power, promising to hold elections in July 2023 and hand over to an elected civilian government.
But opponents, who have taken to the streets, say he has instead put the military firmly in charge. Protests against the military's grip on power have faced a fierce response from Burhan's security forces.
While both Burhan and Hemedti climbed under Bashir, the Islamists who were a pillar of Bashir's rule for three decades are likely to want Hemedti defeated and a victory by Burhan's regular army, putting their military allies back in government.
Pro-democracy groups have said Bashir-era loyalists - sometimes referred to as the "remnants" of the old order - could seek a return on the back of the army's fight with the RSF.
"The remnants' plan and their diligent work is to take control of the country once again, even if this means breaking the country apart," a group that includes the pro-democracy Sudan’s Forces of Freedom and Change Coalition and neighbourhood resistance committees said in a statement.
For now, the battle for Khartoum rages on amid fierce fighting for control of strategic assets such as the airport, army headquarters and state broadcaster.
And neither leader is backing down. Burhan has ordered the RSF paramilitary disbanded and declared it a rebellious group. The military wants the RSF integrated into the regular army and under its controls, two military sources said.
"We know where you are hiding and we will get to you and hand you over to justice, or you die just like any other dog," Hemedti, who has branded Burhan a ‘criminal’ told Al Jazeera TV.