Evidence has emerged strongly suggesting that U.S.-armed rebels have used an American-supplied weapons system to kill a handful of senior Russian military officials in Syria.

Video footage, circulated by a known CIA-backed Free Syrian Army militia, shows a wire-guided BGM-71 TOWs anti-tank missile fired at a rooftop where unidentified uniformed personnel had gathered. The location of the building under attack is likely Latakia province, where the rebels have lately suffered setbacks as a result of intensified Russian airstrikes and artillery shelling aiding forces loyal to Bashar al-Assad’s regime.

Everything is based on open-source intelligence and reporting from Syrian opposition, Turkish, and Russian sources, all of which agree that at least one high-ranking Russian was killed in action in Syria. As of Thursday evening, U.S. officials would neither confirm nor deny to The Daily Beast whether an increase in resupplies to U.S.-backed rebel militias was in the offing as a result of the complete and utter breakdown of Syrian peace negotiations in Geneva.

But if the FSA is indeed taking out Russian commanders with American materiel, then two former Cold War adversaries would find themselves in a miniature replay of the Soviet-Afghan proxy war—exactly the sort of geopolitical brinkmanship that President Obama has repeatedly forsworn. More significantly, such a contingency could derail any creeping efforts at diplomatic reconciliation between Washington and Moscow after a severe breakdown of relations following Russia’s invasion and annexation of Ukraine in 2014.

On Wednesday, the FSA’s Northern Division, one of the 39 anti-Assad militias backed by the CIA, uploaded a video showing one of its soldiers firing a TOW missile at half a dozen or so unidentified uniformed men gathered on a rooftop of a building. The video, uploaded at 5:57 GMT, named the targets as Russian officers but gave no details about the exact location of the attack apart from noting that it was somewhere near Syria’s coast—the region of the country where Russia has recently constructed forward operating bases and airfields. There was little doubt that whoever was on that roof didn’t survive the resulting blast.

About an hour later, Russia’s state-owned TASS news agency reported that a Russian officer who had been advising the Assad’s army had indeed been killed in Syria—not by U.S.-backed rebels but by ISIS, which allegedly hit a military garrison with mortars on Monday. No location for this attack was given.

By 7:23 p.m. Wednesday, an opposition group known as the Revolutionary Forces of Syria appeared to corroborate the Northern Division’s claim and isolated the rooftop blast to the Jabal al-Akrad mountain region of northern Latakia, Assad’s ancestral home where pro-regime forces—helped considerably by Russian airpower and artillery—recently scored a major victory in pushing the rebels out of their main provincial stronghold of Salma. By 8:19, a precise coordinate arrived by way of the pro-opposition Local Coordination Committees, which reported that “15 militants, including 3 Russian officers and 4 Assad’s forces officers [sic]” had been killed by a TOW in Marj Khawkha. This is a village just outside of Salma, where the presence of Russian troops has been confirmed by independent media. Turkey’s Anadolu Agency then picked up the story, specifying that four Russian generals were among 15 officials killed in the Jabal al-Akrad hit. One of the generals was identified only as “Yuri.” All of Anadolu’s claims were attributed to anonymous Syrian opposition sources.

At 8:30 p.m., Aleksandr Kots and Dmitry Steshin, two reporters from the pro-Kremlin newspaper Komsomolskaya Pravda—both of whom gained notoriety for their propagandistic dispatches from the war in Ukraine—cited “unofficial reports” that a Russian officer acting as a military adviser to the Syrian regime had died from multiple shrapnel wounds sustained during a mortar attack outside Salma. This article, however, attributed the attack to Turkish armed forces, relying on what the Syrian Foreign Ministry had evidently told Kots and Steshin. Another Komsomolskaya Pravda journalist gave the unnamed dead Russian’s rank as lieutenant colonel and added that he’d been working in Syria since 2012, training the Syrian military in the use of heavy equipment.

Ever since Turkish F-16s shot down a Russian Sukhoi Su-24 bomber that had briefly entered Turkish airspace on Nov. 24, Moscow has retaliated with information warfare (Putin has accused the NATO member of buying oil from ISIS, something his client in Damascus continues to do), sanctions, canceled pipeline talks, and a high-octane form of deterrence. Russia’s most sophisticated air defense system, the S-400, arrived in Syria not long thereafter.

Part of the impetus for retaking Salma was to deliver a hammer-blow to Ankara’s preferred proxy, ethnic Turkmen rebels who have operated in mountain ranges of Latakia and Idlib provinces. This week, Russia accused Turkey of preparing a military incursion into northern Syria. Mass population displacement also appears part of the Kremlin’s strategy. Seventy thousand Syrian civilians have fled Aleppo’s countryside for the Turkish border since Russia’s sorties intensified in the last few days. The Komsomolskaya Pravda accusation seems consistent with a coordinated anti-Turkish messaging campaign.

Complicating matters further, however, was a report in Russia’s independent newspaper Novaya Gazeta that Igor Konashenkov, the chief spokesman for Russia’s Ministry of Defense, said the officer had died in a hospital Monday from ISIS mortar fire, which also killed four Syrian military trainees. Konashenkov gave no date for the attack, but unnamed sources told the paper that it occurred over a week ago, on Jan. 26. Also, it was at a training center nowhere near Latakia but in Homs City. (There is no known ISIS presence in that city, or within striking mortar range of it.)

This isn’t the first time a Russian serviceman has been killed in combat in Syria. Following the downing of the Russian Su-24 (the pilot of which was killed), a Russian military helicopter, searching for the surviving navigator, was brought down in the mountains of Latakia. Rebel fighters claimed that they had used a TOW missile to strike the helicopter. One Russian marine was killed.

The final piece of evidence was furnished again on Thursday by the Northern Division, which posted a follow-up video interspersing statements from the TOW gunner seen in the original with the raw footage of the attack. An officer from the Northern Division stated on camera: “The Anti-Aircraft Battalion affiliated with the Northern Division got information from the battalion commander that some Russians were scouting in the Turkmen Mountains. We took the [TOW] base and, following the reconnaissance mission, we found a number of Russian soldiers gathered on the rooftop of a building. I dealt with them and one of the dead was a high-ranking Russian officer, alongside some Russian officers and Syrian officers.” This appeared to conform to what the Local Coordination Committees and Anadolu Agency had earlier published.

Qalaat al-Mudiq, a pseudonymous military analyst who studies the Syria conflict, told The Daily Beast that videographic evidence of TOW use on the battlefield had trickled off in the last months of 2015 and totally vanished in the first two weeks of 2016. “The decrease happened after the record number of 115 TOWs recorded in October,” al-Mudiq said. “There were 73 in November and 49 in December. There were no recorded TOW launches in January until the 12th, and that entire month saw only 22 in total.” February has already been a return to prior use frequency. In the first three days of this month, al-Mudiq has already found videos of 16 TOW launches—including the one that purportedly killed one or more Russians in Latakia.

The provision of this munition is both limited and highly regulated. The TOWs are supplied directly by Saudi Arabia, from stocks purchased from the United States, and with an end-user agreement that allows a U.S. veto on where they are used and by whom. According to multiple FSA sources, who spoke to The Daily Beast on the condition of anonymity, rebels are trained in teams of 50 in Jordan, Qatar, Turkey, or Saudi Arabia, but mainly in the first two countries. “After this training, they get back to the border, they get inside Syria, and then they get their gear,” one Jordan-based rebel liaison familiar with the TOW supply chain said. “With the TOW, each 50-man team gets one launcher and five missiles. They’re told to make a video verifying the missiles’ use and bring the spent missile casings to show they haven’t sold them or whatever.”

Approximately 4,000 anti-Assad rebels have gone through this ostensibly clandestine program, the source added, meaning that the total number of TOWs that have already circulated throughout Syria is roughly 400.

TOW recipients are part of a CIA-spearheaded program, featuring 39 select rebel groups, dedicated to fighting the Assad regime and its manifold proxies. The program is coordinated in two joint operations centers, based in Turkey and Jordan, and administered by the intelligence agencies of several Western and regional countries. TOWs have been shown to render the regime’s dwindling stock of Soviet-era armored vehicles into fiery gnarls of metal. Recently, however, these vehicles have been photographed outfitted with a panoramic turret that many observers believe is a missile detection mechanism, which would itself be an indicator of the high toll the weapon has taken on the Syrian Arab Army. Russian T-90 tanks equipped with active anti-missile protection systems also have appeared lately on the frontlines with both Syrian soldiers and Hezbollah paramilitaries.

Rebel recipients of the wire-guided munition have also killed generals and lower-ranking officers from Iran’s Revolutionary Guards Corps, Hezbollah, and Assad’s National Defense Forces, an Iranian-built militia of Shia and Alawite loyalists, under as-yet-undetermined circumstances. Forty IRGC officers were killed in Aleppo in a single month during the regime’s first offensive last November. Yet the recent influx of Russian military “advisers” and now, reportedly, Spetsnaz commandos, has made it all but certain that American proxies would eventually rack up Russian casualties with American-made hardware. There are an estimated 4,000 Russian military personnel stationed in Syria.

The CIA program predates and was always distinct from the now-defunct Pentagon-run “train and equip” mission, which, at a price of $500 million, envisaged a strictly anti-ISIS counterterrorism squad made up of Sunni Arabs and Sunni Turkmen fighters, collectively known as the New Syrian Forces. Train and equip’s recruits all came from U.S.-approved FSA groups, but the program ended in calamity last October after The Daily Beast reported that American military gear including M4 rifles and gun-mounted pickup trucks supplied to the New Syrian Forces’ second graduating class had been passed along to al Qaeda’s Syria franchise Jabhat al Nusra. The commander responsible, Abu Zayd, from the Division 30 rebel group, had himself been “vetted” but not trained by the Pentagon, as U.S. Central Command confirmed.

While the TOW is a signature of America’s involvement in the anti-Assad rebellion, its value to rebels on the battlefield is considered secondary to other known anti-tank systems—all of them, ironically, Russian-made.

“The TOW missiles are not a big deal,” said Isam El Rayyes, the spokesman for the FSA’s Southern Front, a umbrella organization of 35,000 fighters, many of whom are TOW recipients. “It’s less sophisticated than other weapons we have, but it’s gotten a lot of media attention because it’s American.”

The TOWs, El Rayyes noted, are mostly used in Syria’s rural areas against tanks and BMPs parked on country roads, the reason being their limited range. The TOWs given to rebels can travel a maximum of 3.7 kilometers. The fighters consider the Russian Konkur and Kornet missile more effective because missile resupplies for these systems are more readily available—easily seized from regime stockpiles—and they fly farther. The Konkurs rebels have confiscated from Syrian army warehouses can reach up to 5 kilometers.

The Southern Front is supplied by several Western and regional intelligence agencies, all coordinating in the Military Operations Command, or MOC, in Amman. El Rayyes denies that the group’s stream of armaments has dwindled to a trickle as a result of renewed diplomatic pressure to cajole the Southern Front into attending peace talks in Switzerland, as has been reported mainly in the pro-Assad media. Rather, he says, MOC-licensed resupplies have remained as low as they ever were.

The Southern Front has never been adequately equipped by its backers for fear that it might actually succeed in achieving a military solution to a conflict that Washington insists has only a political terminus. But the front’s constituent militias have suffered heavily from Russian airstrikes in the last two months. Since Nov. 28, the Russians have carried out more than 800 sorties in Deraa province alone, forcing the rebels’ loss of the town of Sheikh al-Maskeen. The indiscriminate bombing campaign, analyzed and denounced by human-rights monitors, has displaced an estimated 150,000 civilians.

“These airstrikes are like hell,” El Rayyes said, adding that there’s now a new pro-regime offensive being pressed in Atman, a town just north of Deraa City. “We’ve had 60 Russian bombing raids in 24 hours. The FSA controls Atman exclusively. There is no Nusra or Islamist groups here.”

The last 48 hours has seen one of the worst setbacks for the Free Syrian Army since the armed uprising against Assad began almost five years ago. Backed by Russian airpower, loyalist forces led by Hezbollah and Shia militias have managed to sack several strategically crucial settlements in northern Aleppo province, including Hardatnin, Bashkoy, and Mayer, thereby cutting off FSA supply lines from southern Turkey to Syria’s industrial heartland. Aleppo City is all but encircled. “They have not stopped bombing,” a rebel leader withdrawing from Hardatnin told the Guardian on Thursday. “All the hospitals have been destroyed. We have around seven attacks an hour every day for a week. There were more than 120 on Tuesday alone.”

On Wednesday, Pentagon spokesman Col. Steve Warren told reporters that a mere 10 percent of all Russian airstrikes have gone after ISIS targets—and then only when ISIS has come into direct confrontation with pro-regime forces. “The Russians at this point have made it very clear that their offensive operations… are in support of Bashar al-Assad and his regime. So when the regime is fighting, whoever the regime is fighting, that’s who gets struck.”