WHETHER Donald Trump likes it, or not, the US is the free world’s policeman.

Never have we needed this commitment more than in today’s turbulent times.

So, the President’s decision to leave his allies, the Kurdish Syrian Defence Force (KSDF), to the mercy of a Turkish onslaught is incomprehensible after they’ve done most of fighting against Islamist extremists.

The Kurds have thousands of these fighters under lock and key, but for how much longer?

This appalling situation was precipitated by Mr Trump’s decision to withdraw American troops from northern Syria.

It gave Turkey’s President Erdogan the green light to attack an ethnic minority he calls terrorists.

Understandably, Kurdish troops guarding ISIS prisoners are leaving to face the Turks.

In defending his decision, Mr Trump has only rubbed salt in the wound by saying the Kurds “didn’t help us in the Second World War”.

Even senior serving US officers in the region are speaking of feeling “ashamed”.

One desperate Syrian Kurdish leader said: “You are leaving us to be slaughtered.”

He’s probably right.

The KSDF has now sought help from Syrian President Assad, who is in turn backed by Russia and Iran.

This raises the stakes significantly and Mr Trump’s blustering threats to bankrupt Turkey with sanctions have met with defiance from President Erdogan.

In return, he’s threatened to send 3.6 million Syrian refugees, currently held in Turkish camps at the EU’s behest, back to European shores.

While Mr Trump’s justification, that the US has no business in Syria, may appear valid to the folks back home, his actions have made the Middle East more unstable, given free rein to the Russians, and worse Iran, and left Kurdish civilians facing genocide.

Diplomacy by Twitter has a lot to answer for.