The pledge from Nato chief Jens Stoltenberg came as Russian warplanes and Assad forces intensified their offensive against rebels

Nato has put thousands of troops on standby, ready to be sent to Turkey to protect the country in the face of Russia’s escalating military campaign across the border in Syria.

The pledge from Jens Stoltenberg, the Nato chief, came as Russian warplanes and Assad regime forces intensified a co-ordinated offensive against Syrian rebels yesterday. Ash Carter, the US defence secretary, said the Russians had initiated the offensive — “shattering the façade they are there to fight Isis”.

Mr Carter predicted that Russia’s ­intervention would come at a price: “This will have consequences for Russia itself which is rightly fearful of attacks . . . in coming days, the Russians will begin to suffer casualties.”

Russian aircraft have made multiple incursions into Turkish airspace in