The Irish Times view on the Syrian crisis: Trump’s historic mistake

Donald Trump says he will support imposing tough sanctions on Turkey for doing something he facilitated Ankara to do last week. The US president's hopelessly confused message is no doubt partly a result of his own surprise at the backlash within Republican ranks over a decision that enabled Turkish president Recep Tayyip Erdogan to invade northern Syria and establish a "buffer zone" along the border. But it is also of a piece with an ill-considered, self-defeating decision that harms America's interests and puts thousands of lives at risk – all so that Trump can claim to be making good on his campaign promise to extricate US troops from "endless wars".

The only surprising thing about the descent into chaos that Trump's decision precipitated is how quickly it has happened. Having been betrayed by their US ally after fighting – and dying – in a long and ultimately successful war against Islamic State, the Syrian Democratic Forces, a Kurdish-led militia, announced on Sunday it had agreed a deal with Bashar al-Assad, Washington's sworn enemy, to jointly repel Turkish-backed forces advancing south. Those forces' indiscriminate artillery fire is already spreading chaos in a region that had been relatively calm for more than a year. Islamic State stands to benefit from the new instability; hundreds of its supporters are said to have fled from one Kurdish-run detention camp in the region, and US troops reportedly left behind dozens of "high-value" jihadist prisoners as they fled the crossfire in recent days.

Trump is hardly the only blameworthy player. European states have refused to take back their Islamic State fighters, seeking to wash their hands of the problem. Russia and Iran have played destabilising roles in Syria for years, while Erdogan himself, having facilitated the growth of Islamic State, is now sending Syria back to the abyss. But Trump's decision is a historic mistake. In one move, he has betrayed the Kurds, cemented Assad's future, relinquished all US leverage in Syria, given Russia a strategic victory and breathed new life into Islamic State.