U.S. Secretary of State John Kerry has just phoned Russian Foreign Minister Sergei Lavrov warning him not to "escalate the conflict" by increasing Moscow's military support for the beleaguered Syrian regime. He stamped his foot quite hard, telling Lavrov that his government's actions could "lead to greater loss of innocent life, increase refugee flows and risk confrontation with the anti-ISIL [Islamic State] coalition operating in Syria."
What the Russians have actually done, so far, is to send an advance military team to Damascus of the sort that is normally deployed to prepare for the arrival of a much larger military force. They have also sent an air traffic control center and housing units for its personnel to a Syrian air base.
It suggests that Moscow is getting ready to go in to save President Bashar Assad's regime. It has given Assad diplomatic support, financial aid and some weapons over the course of the four-year-old Syrian civil war, but it will take more than that to save him now. That would include at least an airlift of heavy weapons, but maybe also direct Russian air support for Assad's exhausted troops.