Did U.S. weapons supplied to Syrian rebels draw Russia into the conflict?

The U.S.-made BGM-71 TOW missiles were delivered under a two-year-old covert program coordinated between the United States 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. And in recent days they have been used with great success to slow the Russian-backed offensive aimed at recapturing ground from the rebels.

Since Wednesday, when Syrian troops launched their first offensive backed by the might of Russia’s military, dozens of videos have been posted on YouTube showing rebels firing the U.S.-made missiles at Russian-made tanks and armored 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 claim they took out 24 tanks and armored vehicles on the first day, and the toll has risen daily since then.