If there is one conclusion to be drawn from US President Donald Trump’s capricious handling of the problematic issue of Kurdish forces in Syria, it is that the American leader has no interest in maintaining alliances once they have outlived their usefulness.
After the prominent role the Kurdish-led Syrian Democratic Forces (SDF) played in defeating ISIS, there was a general acceptance among their western allies that they should continue to be supported.
Without their bravery and sacrifice, ISIS would still be controlling large swathes of Syria and continuing its barbaric rule. Instead, ISIS’s self-proclaimed caliphate is no more, and an estimated 75,000 ISIS fighters and their dependents are languishing in a network of Kurdish-run detention centres.
And yet, for all the efforts of the Kurdish People's Protection Units (YPG), who played a prominent role in the SDF's campaign against ISIS, the Kurds now find themselves on the receiving end of a Turkish military assault on Kurdish-controlled territory in northern Syria – and all because of an overnight deal struck between Mr Trump and Turkish President Recep Tayyip Erdogan at the weekend.
The Turks have long-harboured ambitions of seizing control of Kurdish-held territory in northern Syria. Hostilities between Ankara and the Kurds in this hotly-contested area have been going on for decades, with Turkey at one point, prior to the Syrian civil war, threatening to declare war on Damascus in their desperation to crush Kurdish hopes of self-rule.
This was at the time when the PKK, a Marxist group widely condemned in the West as a terrorist organisation, was active in carrying out a string of terror attacks against Turkey.
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These days – at least in the eyes of the Turks – the PKK has been replaced by the YPG, the group representing Syrian Kurds that pursues the same separatist agenda.
Turkey’s hostility to the YPG is even said to have resulted in Ankara clandestinely supporting militant extremist groups in Syria – a suggestion Turkey refutes – in the hope that they would defeat the Kurdish forces.
Now, thanks to Mr Trump's surprise, and unilateral, decision to allow Turkey to create a so-called safe zone in northern Syria, the Kurds find themselves under direct attack from Turkish forces.
After Turkey launched its military offensive, codenamed “Operation Peace Spring”, on Wednesday, Turkish forces are reported to have attacked at least 181 targets in Kurdish-controlled territory, while the Kurds have responded by withdrawing fighters currently deployed fighting ISIS to help defend Kurdish territory against the Turkish assault.
Mr Erdogan has said that the aim of the Turkish assault is “to prevent the creation of a terror corridor across our southern border, and to bring peace to the area.”
The Turkish action, though, has drawn strong condemnation from Europe, with Britain leading calls for an emergency meeting of the UN Security Council. The EU called for an immediate stop to the attack, warning it would "undermine the stability of the whole region".
Concern has also been expressed about the fate of the ISIS captives, with fears that they might be able to escape and rejoin ISIS as the attention of their Kurdish guards is diverted to tackling the Turkish advance. Prior to the Turkish move, the US took the precaution of taking into American custody two high-profile ISIS fighters of British origin – members of the so-called Beatles terror cell – who are accused of torturing and murdering Western hostages during the caliphate.
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Nor has Mr Trump escaped criticism at home for his part in giving Ankara the green light to mount its offensive. A number of prominent Republicans have denounced his decision, accusing him of betraying America’s erstwhile allies in the SDP. Lindsey Graham, a Republican senator close to Mr Trump, said the White House had "shamelessly abandoned" the SDF to the Turkish attack. "I urge the president to change course while there is still time.”
To judge by the latest presidential tweets, though, it seems Mr Trump is completely unrepentant, playing down the significance of the US-Kurdish relationship on the somewhat bizarre grounds that “they didn’t help us with World War 2”. This was very much in keeping with the tenor of an earlier tweet in which he stated, “The Kurds fought with us, but were paid massive amounts of money and equipment to do so.”
What this reveals about the American president’s thinking is that he views alliances in purely transactional terms. Thus, in the case of the Kurds, they are valuable to Washington so long as they have a role to play in defeating ISIS. But once this objective has been achieved – Mr Trump has already declared victory in the war against ISIS – then the alliance no longer serves any purpose, and former allies can be disposed of with impunity.
Mr Trump, who makes no secret of his “America First” outlook, may think this is the best way to conduct foreign policy, but it is likely to cause deep unease among Washington’s traditional allies who look to the US to safeguard their interests in return for supporting American policy, but now find themselves dealing with a president who is clearly uninterested in maintaining America’ traditional way of doing business with its allies.
Mr Trump’s primary interest, it appears, is himself, and with his main focus now on winning re-election in next year’s presidential election contest, his focus is steering clear of any foreign entanglements that might work against him.
It is for this reason that Washington’s response to the recent attacks on Saudi Arabia’s oil infrastructure has been so modest. Even though all the available evidence points to Iran’s involvement in the attack, the White House has proved reluctant to take robust measures in response.
It was a similar picture when Iran shot down a US Navy drone over the Strait of Hormuz in the summer, an attack deemed to by an act of war by the American military.
For the bottom line with Mr Trump is that he is only interested in making decisions that win him votes at home. And, in terms of winning the US presidential election contest, Mr Trump has clearly decided there are no votes to be won from maintaining his alliance with the Kurds.
Con Coughlin is the Telegraph’s defence and foreign affairs editor