Here’s a scenario of how the Syria war and larger Middle East instability could escalate into something much worse.

As in imperial Europe in the period leading up to the First World War, the collapse of an entire order in the Middle East is in process, while forces long held in check are being released. In response, the former superpowers of the Cold War era have once again mobilized, at least modestly, even though both are fearful of a spark that could push them into direct conflict. Each has entangling regional relationships that could easily exacerbate the fight: Russia with Syria, the US with Saudi Arabia and Israel, plus NATO obligations to Turkey. (The Russians have already probed Turkish airspace and the Turks recently shot down a drone coyly labeled of “unknown origin.”)

Imagine a scenario that pulls any of those allies deeper into the mess: some Iranian move in Syria, which prompts a response by Israel in the Golan Heights, which prompts a Russian move in relation to Turkey, which prompts a call to NATO for help… you get the picture. Or imagine another scenario: with nearly every candidate running for president in the United States growling about the chance to confront Putin, what would happen if the Russians accidentally shot down an American plane? Could Obama resist calls for retaliation?

As before World War I, the risk of setting something in motion that can’t be stopped does exist.

As I’ve said before, I don’t think any of this is Obama’s fault, but if it does ultimately lead to something very bad, the roots may be traced back to events that happened on his watch whether they were under his control or not (also, clearly, to direct actions taken by his predecessor), and his legacy could be the president who let the post-World War II and post-Cold War order slip away.