President Bashar al-Assad’s forces are making a new push in southern Syria with the help of Russian air cover in a move that could not only weaken one of the country’s remaining rebel strongholds, but also threaten the balance of power on a combustible border with Israel.

The growing Russian role in the south has surprised many regional diplomats who believed Moscow had an understanding with Syria’s southern neighbours, Jordan and Israel, not to extend into their sphere of influence.

Rebels from Syria’s Southern Front alliance say they too were surprised to become the target of the new campaign: their forces are directly supplied by the Military Operations Command (MOC), an operations room staffed by Arab and western military forces, including the US. […]