he is just reacting to the situation. Unfortunately his decisions are not very wise and could lead to war. He is being played. I think the real target is Russia-China. Everybody knows that Russia will never allow a no-fly zone in Syria. If the US imposes a no-fly zone without the UN THEN we will have a serious problem. This means that international law will be broken. This could really lead to a bigger war. Even nuclear war; President Medvedev said so himself:
Of course he didn't mention Syria, I think he was referring to Nato's ABM system. But like the ABM-Shield in europe, a US-invastion in Syria is treated as a threat to Russian interesteds. It is Russia's backyard.