Ian Black writes: Syrian military weakness, painfully exposed over the last few months, is the main reason for direct Russian intervention in the war – whether its goal is to strike at Islamic State or, more likely, to take on any rebel force fighting Bashar al-Assad in order to shore up his position and stave off demands that he step down.

Officials and analysts say Moscow decided to deepen its involvement after the fall of the northern towns of Idlib and nearby Jisr al-Shughour in May served as a “wake-up call” about the parlous state of the Syrian army. Both were taken by the Jaysh al-Fateh (the Victory Army), a coalition of Islamist rebels.

Russia’s move was prompted in part by Assad’s other main ally, Iran, which plays a powerful though discreet role in Syria but is usually reluctant to commit its own forces. “The Iranians told the Russians bluntly: if you don’t intervene, Bashar al-Assad will fall, and we are not in a position to keep propping him up,” said a Damascus-based diplomat. [Continue reading…]