The US has been training, equipping, and backing the SDF rebels in Syria's civil war for years as Russian Federation has provided similar assistance to forces loyal to the Syrian government in close proximity.
More than 200 contract soldiers, mostly Russians fighting on behalf of Syrian leader Bashar al-Assad, died in a failed attack on a base held by USA and mainly Kurdish forces in the oil-rich Deir Ezzor region, two of the Russians said.
As we reported at the time, USA military officials say they were in contact with Russian counterparts during the attack and were assured that Russia would not engage coalition forces in the vicinity.
The incident shines a light on a little-known weapon in the Kremlin's hybrid-war arsenal.
Russia has backed Syria's fight against terror since late 2015 when Russian air force and troops arrived in the Arab country at an official request of Damascus to help the government fight against Daesh and other Takfiri militants.
Of course, if indeed Russian soldiers were killed while fighting under covert circumstances - in the same way as killed U.S.
President Vladimir Putin's spokesman, Dmitry Peskov, wouldn't comment on the reports either, saying they needed to be verified.
Wagner is made up of detachments that may be controlled by Yevgeny Prigozhin, a wealthy businessman who's been dubbed "Putin's Cook" because his company provides catering services to the Kremlin, according to the Fontanka news service.
Russian media also cited unconfirmed claims that overall casualties could be as high as 200, the majority Russians. They said the deconfliction line was still operating and Russian Federation so far hadn't protested the decision to launch the air strikes.
At no point, a US military spokesman said, was there any chance of direct conflict between USA and Russian ground forces. It's not clear who was paying the soldiers of fortune, whether it was Russian Federation directly, its allies in the war, Syria and Iran, or a third party.
Around 600 fighters with artillery and tanks, most Russian-speakers, took part in the attempt to storm the base, according to one of the people familiar with the matter. "Russian officials assured coalition officials they would not engage coalition forces in the vicinity".
The incident appears to be the first publicly known case of the USA military firing on and killing Russians fighting on behalf of Syrian President Bashar al-Assad. It's also the most visible manifestation of American-on-Russian violence, even if the erstwhile Cold War adversaries were not technically engaged against each other.
The Russians claim a handful of Russian "paramilitary contractors" were killed in the battle, while the Syrian government says US troops and their allies killed nearly a hundred Russians.
"Coalition officials were in regular communication with Russian counterparts before, during and after the thwarted, unprovoked attack", said Col. Ryan Dillon, a spokesman for the us military.
Wagner's troops in Syria, which have numbered up to 2,000, took part in fighting to reclaim the ancient city of Palmyra in 2016 and 2017. Afghan war will cost B in 2018 United States expands air campaign to northern Afghanistan Mattis defends plans for new nuclear capabilities MORE described the attack as "perplexing".
They were deployed both to help keep the official cost down and to avoid reports of casualties, especially with a March presidential election in Russian Federation fast approaching, analysts have said. They are believed to be dead, according to Russian officials.