Tweet rings alarm bells around the world

to leave Syria — and there are still about 1,000 remaining there — was December last year. It brought the immediate resignation of former marine general Jim Mattis as defence secretary. This time, the move potentially abandons Kurdish allies to their fate — and the backlash from the Republican Party was swift.

Trump’s tweeted reasons for pulling out are specious. He said the US could not get involved in “ridiculous tribal wars” endlessly, and that the US had led the “100 per cent” recapture of Syrian territory from IS.

This is certainly not true because there are thousands of jihadis, many of them hardened fighters, around the border zones of Syria and Iraq. The battle with the militants is far from over.

It is the ditching of the Kurds, and the tilt towards the aggressive stance of Erdogan, that has alarmed soldiers and politicians alike in Washington. Erdogan has announced his troops are ready to move against the Kurds of the YPG, whom he regards as “terrorists” of the PKK ( the Kurdish Workers Party) in thin disguise.

This would mean thousands of IS prisoners in Kurdish camps would be released — and Europeans among them have threatened to come home and do their worst.

A Turkish move would mean further war affecting millions of refugees inside and outside Syria. The Pentagon has since briefed that only about two dozen US forces have been pulled from the Syrian-Turkish border. Trump’s retreat by tweet goes much wider.

It is part of the drift of his mind and sympathy from key allies in the Middle East.

He has said and done little following the devastating drone and rocket attack sponsored by Iran on Saudi oilfields last month.

After his tough talk and cancelling the 2015 nuclear deal with Iran, there has been little follow-up. The presidential mind has wandered on.