Putin is trying to contain the US who are clearly the aggressors here. Both the US and Israel have been firing on Syrian troops. Down by the Euphrates the Kurds are allied with the US and are firing on Syrian troops on the West bank. Meanwhile in Afrin the Kurds are calling on the support of the Syrian troops against Turkey. Meanwhile Turkey is completely getting away with this as who can stop them? The consequences of the US firing on a fellow NATO member could be considerable.