Alexander Zakharchenko, who was killed in an explosion in the self-proclaimed Donetsk people's republic on Friday, had led Russian-backed insurgents in the rebel region for the last four years.
The son of a local miner and a former businessman, Zakharchenko became the rebel prime minister in August 2014, taking over from a series of Russians who had held the post.
This was apparently a move to bolster Kremlin claims that the rebellion was purely a local affair.
The former field commander, who died at the age of 42, would dress in khaki military fatigues even when dealing with civilian problems in the war-wrecked region.
He was wounded in the foot in fighting in the town of Debaltseve in 2015 but outlived many of the other rebel commanders.
In a region dominated by coal mining, Zakharchenko briefly worked as a mine electrician before going into business connected to the industry.
But he sold his business in 2014 to finance the rebels and took part in the storming of the regional administration building in Donetsk that launched the conflict in April that year.
In November 2014 he was elected the first president of the Donetsk republic after winning 75 percent of the vote in controversial polls, facing no real opposition.
At the time, he denied claims from Kiev that Russian troops were taking part in the fighting.
He agreed a number of fragile and frequently violated ceasefires in fighting with Ukrainian forces that has killed more than 10,000 people.
- Soviet-style parades -
Zakharchenko introduced Soviet-style military parades with tanks in Donetsk and told AFP in 2015 that he regretted the break-up of the Soviet Union.
"The Soviet Union was a great country and it was a huge mistake that it was destroyed by the CIA and other secret services," he said.
"Europe and other countries were scared stiff of us," he added.
One of his "consultants" was a well-known Russian novelist with nationalist views, Zakhar Prilepin.
He accused the Ukrainian military and special forces of conducting attacks on key rebels, many of whom have died in similar blasts in the region.
The killing in 2016 of notorious rebel commander Arseny "Motorola" Pavlov, he said, was a declaration of "war".
The former leader of the Lugansk rebel region, elected at the same time as Zakharchenko, resigned last year.
In 2017 Zakharchenko announced plans to create a new "state" to replace Ukraine called Malorossiya (Little Russia) -- a tsarist-era term for an area covering much of modern day Ukraine -- that would have its capital in Donetsk.
The other rebel bosses rejected it, however, and the insurgents' backers in the Kremlin dubbed it a "private initiative".
This month in an official rebel television news show devoted to his activities, Zakharchenko told a rebel legion that "we live in a difficult, unique time. On the one hand this is a tragic time, on the other hand I am glad to have known all of you".
"We went into attack together and dreamt together how we will live in a new happy country," he said.