February 16, 2018 London—On three different Syrian front lines, the violent events of recent days signal that the long-running conflict has reached a critical moment of evolution, as key players jockey to establish new red lines and maximize gains after the defeat of the so-called Islamic State.

First to grab headlines was the launching last weekend of an Iranian drone from western Syria into Israel for the first time. Israel shot it down, then lost one of its own F-16 jet fighters – the first such loss in decades – to a Syrian anti-aircraft missile after striking the drone’s home base.

The Israeli Air Force retaliated for the downed jet, targeting