As Ukrainian troops gained ground in the country's east in early July, separatist leader, Aleksander Borodai, a Russian national, left for Moscow for political consultations.
After what he described as successful talks with unnamed people there, he returned to the rebel stronghold of Donetsk to introduce a new senior figure in his self-proclaimed republic, a compatriot seasoned in the pro-Russian separatist movement in Moldova and a war between Russia and Georgia.
Vladimir Antyufeyev was named "deputy prime minister" by Borodai on July 10, one of several native Russians to have taken charge of the separatist rebellion in Ukraine's eastern regions.
Joining Borodai and rebel commander Igor Strelkov, Antyufeyev's arrival underlines a change at the top of the separatist movement, highlighting Moscow's involvement in the conflict, Western officials say. The Kremlin denies any involvement.
"There has been a dramatic change in the leadership of the Donetsk People's Republic over the past weeks, which certainly gives the impression of a much more hands-on Russian directive role," said Geoffrey Pyatt, the U.S. ambassador to Ukraine. "These individuals are in regular touch with authorities in Russia."
Ukrainian-born rebel leaders have been eased out, causing rifts among increasingly nervous separatists since a Malaysian airliner was downed over rebel-held territory just over a week ago.
Antyufeyev replaced Donetsk native Alexander Khodakovsky as the top security person in the self-proclaimed Donetsk People's Republic. Denis Pushilin, another local once titled the republic's president, was dismissed.
Khodakovsky remains a top commander but has taken an increasingly independent line, telling Reuters that separatists had the type of anti-aircraft missile system that Washington says brought the plane down, killing all 298 people on board.
Borodai denied this assertion.
A Ukrainian official in the southern Azov Sea port city of Mariupol, which Kiev reclaimed from rebels last month, said Russians were taking over the entire rebel operation, sidelining or removing locals.
Antyufeyev, also known as Shevtsov
Antyufeyev, also known as Vadim Shevtsov, has a history of supporting pro-Russian separatist movements in the former Soviet Union and brings a tough discipline and doggedness to the campaign in eastern Ukraine.
The balding 63-year-old says he "fought national fascism" by supporting separatists in the pro-Russian self-procalimed republic of Transdnestr in neighboring Moldova and in the breakaway regions of South Ossetia and Abkhazia in Georgia.
At his new office at the separatists' Donetsk headquarters, the Siberian-born Antyufeyev said he came to Ukraine because Russians were being killed by forces sent from Kiev.
"I know what it is to fight for the rights of the people. … I know what hot spots are," he said in an interview. A picture of President Vladimir Putin looked down on the table where he sat.
Asked whether there were divisions among the rebels, Antyufeyev said: "I am the authority. I have no problems. … If they do not understand that, that is their problem. I am a professional in making [people] understand."
He earned a fearsome reputation when he served in Transdnestr, which split from Moldova in 1990, as the head of security operations for 20 years.
Dismissed in 2012 when his ally was replaced as leader of the tiny sliver of land, he barricaded himself for three days in his study and refused to leave.
The EU first blacklisted Antyufeyev over his role in Transdnestr in 2004. Though it later suspended that decision, it has now blacklisted him again over Ukraine, imposing assets freezes and a travel ban on him.
One person who had been questioned by Antyufeyev in Transdnestr on suspicion of spying for Moldova said he was a tenacious interrogator. Speaking on condition of anonymity, for fear of reprisal, the person said Antyufeyev was "a professional," capable of being sociable and polite, always rigidly following the chosen line. With a smile on his face, Antyufeyev would exert moral pressure, the person said.
Oazu Nantoi, a Moldovan political analyst and expert on Transdnestr, predicted Antyufeyev would aim to further destabilize Donetsk and impede Kiev's efforts to regain control.
"He is no romantic who came to fire a few shots. He knows what his tasks are. Just as he did in Transdnestr," he said. "Antyufeyev knows how to operate in such situations, how to suppress opposition and dissent … create an atmosphere of fear in which people will support any action by the separatists."
Washington says the influx of Russians into the upper ranks of the separatists is matched by an increased number of heavy weaponry coming across the Russian border into Ukraine, a response to advances made by the Ukrainian army on the ground.
Though Borodai insists the separatists' weaponry comes from depots they overran while seizing territory, he admits "volunteers" from Russia keep on reinforcing the rebels' ranks.
He calls his Russian trio volunteers and says their presence in the Donetsk region, or Donbass, is proof of the Russian nation's support for the separatists' cause.
"The people of Donbass rose on their own. It is normal and natural that we ended up heading this movement because of certain competences, our abilities," he told a news conference in Donetsk earlier this month.
"There will be more and more people from Moscow in the DNR [Donetsk People's Republic]," said Borodai, flanked by Strelkov and Antyufeyev.
The stout Borodai denies having ever worked for the Russian security services though admits knowing many people there because of his past work as a "professional political expert."
He and Strelkov say they first met in 1996 in the Russian region of Chechnya, where Moscow has waged two wars against Islamist separatists since 1994. Borodai says Strelkov has long been his "very good acquaintance."
Both said they served in Transdnestr and, more recently, in Crimea. The West says they were aides to the pro-Russian separatist leader of the Black Sea peninsula who was instrumental in Moscow's annexation earlier this year.
The two are on both the EU and U.S. sanctions list. Kiev and the EU say Strelkov, whose real name is Igor Girkin, in fact served in Russia's GRU military intelligence.
Strelkov says he served at the rank of colonel in Russia's FSB security service until quitting at the end of March, and has had battlefield experience in Transdnestr, in Bosnia's conflict and in both Chechen wars.
While he commanded rebel forces in Slovyansk, the town became a citadel of fierce resistance where at least two Ukrainian military helicopters and one warplane were brought down, giving him a hero status among separatists.
Abandoning Slovyansk to Kiev's troops on July 4 to 5 has, however, dented his reputation and upset some rebels.
Strelkov's acquaintances and former colleagues say he developed a reputation as an uncompromising idealist while with the FSB, though his "difficult" character may have been behind what they say was in fact his dismissal from the service.
They say the ouster of Ukraine's former, Moscow-allied President Viktor Yanukovych and Kiev's pivot to the West was a turning point for him.
An acquaintance in Moscow, speaking on condition of anonymity because of the sensitivity of the topic, said Strelkov was outraged by the events in Kiev and believed Russia must not lose Ukraine. The acquaintance added that Strelkov knew Borodai in Moscow and the two helped one another in business. Strelkov left his home in a Moscow suburb in February traveling to Crimea where he occupied the regional parliament along with other fighters shortly before Russia annexed the predominantly ethnic Russian region.
He said people he had known from Crimea then asked him to come to eastern Ukraine.
According to his former colleagues at the FSB, successor to the Soviet KGB, one of his favorite books was the Soviet-era science fiction novel "Hard to be God" — a tale of an agent on a mission to a different planet.