If you want a glimpse of a post-American world, look at Syria. US president Donald Trump said recently: “Let the other people take care of it now.” He may briefly have changed his mind after last week’s alleged chemical weapons attack. But his die is cast.

Six years after his predecessor Barack Obama said Bashar al-Assad must go, the world’s most brutal dictator is more secure than ever. Syria’s future will be settled by Russia, Iran and Turkey — the first two of which want to keep the Syrian president in power. Whatever Mr Trump thinks of the region — on the rare occasions he is forced to do so — is likely to change next week. Even if the US’s missiles are “nice and new and ‘smart!’” as Mr Trump tweeted on Wednesday, the country’s disengagement will resume.

Mr Trump is a symptom, not a cause, of US global fatigue. Its key Middle Eastern turning point came at two moments at the start of this century. The first was when Bill Clinton unsuccessfully attempted to broker a deal between Israel and the Palestinians. Had the deal stuck, it would have excised the deepest Arab complaint against the US — and the region’s strongest excuse for domestic repression. The idea that Mr Trump could pull a two-state deal out of the hat was far-fetched before he said he would move America’s embassy to Jerusalem. Now it is a joke.