American anti-tank missiles supplied to Syrian rebels are playing an unexpectedly prominent role in shaping the Syrian battlefield, giving the semblance of a proxy war between the United States and Russia, despite US President Barack Obama's express desire to avoid one.
The US-made BGM-71 TOW missiles were delivered under a two-year-old covert programme co-ordinated by the US and its allies to help vetted Free Syrian Army groups in their fight against President Bashar al-Assad. Now that Russia has entered the war in support of Assad, they are taking on a greater significance than was originally intended.
So successful have they been in driving rebel gains in northwestern Syria that rebels call the missile the "Assad Tamer" a play on the word Assad, which means lion. In recent days they have been used to slow the Russian-backed offensive aimed at recapturing ground from the rebels.
Since last Thursday, when Syrian troops launched their first offensive backed by Russia's military, dozens of videos posted on YouTube have shown rebels firing the missiles at Russian-made tanks and armoured vehicles belonging to the Syrian Army. Appearing as twirling balls of light, they zigzag across the Syrian countryside until they find and blast their target in a ball of flame.
The rebels say they took out 24 tanks and armoured vehicles on the first day, and the toll has risen daily.
"It was a tank massacre," said captain Mustafa Moarati, whose Tajamu al-Izza group says it destroyed seven tanks and armoured vehicles on Thursday.
New supplies arrived after the Russian deployments began, he said, and the rebels' allies have promised further deliveries soon, bringing echoes of the role played by US-supplied Stinger anti-aircraft missiles in forcing the Soviet Union to withdraw from Afghanistan in the 1980s.
The hits also plunged Washington into what amounts to a proxy war of sorts with Moscow, despite Obama's insistence this month that "we're not going to make Syria into a proxy war between the United States and Russia".
"It's a proxy war by happenstance," said Jeff White of the Washington Institute for Near East Policy, who counted at least 15 tanks and vehicles destroyed or disabled on one day. "The rebels happen to have a lot of TOWs in their inventory. The regime happened to attack them with Russian support. I don't see it as a proxy war by decision."
Whether it becomes one is one of the key questions confronting the Obama Administration after Russian President Vladimir Putin's decision to support Assad's regime.
The TOW missile programme overseen by the CIA is separate from a failed programme run by the Pentagon that was intended to influence the outcome of the other war in Syria, against Isis (Islamic State) in the northeastern part of the country.
The CIA programme got under way before the Pentagon one, in early 2014, with the goal of propping up the flagging rebellion against Assad's rule by delivering training, small arms, ammunition and the anti-tank missiles, which have proved instrumental in eroding the regime's key advantage over the lightly armed rebel force - its tanks and heavy armour.
Supplied mostly from stocks owned by Saudi Arabia, delivered across the Turkish border with CIA approval, the missiles were intended to fulfil another of the Obama Administration's goals in Syria - Assad's negotiated exit from power. The plan, as described by White House officials, was to exert sufficient military pressure on Assad's forces to persuade him to compromise - but not so much that his Government would precipitously collapse and leave a power vacuum.
Instead, Russia intervened to shore up the struggling Syrian Army.
"A primary driving factor in Russia's calculus was the realisation that the Assad regime was militarily weakening and in danger of losing territory in northwestern Syria. The TOWs played an outsize role in that," said Oubai Shahbandar, a Dubai-based consultant who used to work with the Syrian opposition. "I think even the Americans were surprised at how successful they've been."
It was no accident, say US officials and military analysts, that the first targets of Russian airstrikes in Syria were the locations where the rebels armed with TOW missiles have made the most substantial gains and where they most directly threaten Assad's hold over his family's heartland in the coastal province of Latakia.
Those areas were also where the first offensive since the Russian intervention was launched, with Syrian armoured vehicles and tanks setting out from government strongholds into the provinces of Hama and Idlib.
It is unclear whether the TOWs will change the course of the war, as did the Stinger anti-aircraft missiles introduced in the 1980s by the CIA in Afghanistan, used by mujahideen to shoot down Russian helicopters and paralyse the Soviet Army.
Now that the Russians have introduced more intensive airstrikes and, for the first time, combat helicopters seen in videos strafing villages in the Hama area, the TOW missiles may only be able to slow, but not block, government advances.
The rebels have appealed for Stinger missiles or their equivalents to counter the new threat from the air, but US officials say that is unlikely. The US has repeatedly vetoed past requests from the rebels, and their Turkish and Saudi allies, for the delivery of anti-aircraft missiles, out of fear they could fall into extremist hands.
Saudi Arabia, the chief TOW supplier, has pledged a military response to the Russian incursion and rebel commanders say they have been assured more will arrive imminently.
The missiles are delivered in limited quantities and the rebel groups must return used canisters to secure more, to avoid stockpiling or resale.
The system appears to have helped prevent the missiles from falling into extremist hands. Robert Ford, who was serving as US envoy to Syria when the programme got under way, said he was aware of only two TOWs obtained by the al-Qaeda affiliate Jabhat al-Nusra.
"Nusra made a big public display of having these two missiles," said Ford, now a fellow at the Middle East Institute. Had they acquired more, he said, "they would be using them now".
Because end-user agreements require that the buyer inform the US of their ultimate destination, American approval is implicit, said Shahbandar, a former Pentagon adviser.
"It doesn't need an American green light. A yellow light is enough. It's a covert effort and it's technically deniable, but that's what proxy wars are."