Last month, I crossed the Tigris from Iraq into what has become the Autonomous Administration of North and East Syria (NES), which is secured by Britain’s principle ally in Syria and the decisive member of the international coalition against Islamic State.

In a region without good guys, the Syrian Democratic Forces (SDF) are the closest thing to it. They have secured a peaceful corner of Syria, which is building a society based on democratic, communitarian and feminist principles east of the Euphrates.

In August, the SDF agreed to a ‘security mechanism’ with Turkey and the US, who were concerned about SDF cooperation with the Kurdistan Workers’ Party (PKK). The SDF duly pulled back between five and 14 km at different sections along the 400km border and allowed joint Turkish and US patrols of their territory.

SDF commander General Mazlum Abdi, who is responsible for 80,000 Arab and Kurdish troops, told me that he had accepted the buffer to forestall a new war. More than any other person on Earth, General Abdi is responsible for the defeat of Islamic State, the genocidal death cult that once threatened Damascus and Baghdad. His troops have been fighting and dying in their thousands to defeat an enemy unknown in this region until the ill-conceived US and UK invasion of neighbouring Iraq.

The US has relied on the SDF to clean up the mess and now, through a hastily-arranged White House statement, it has signalled that Turkey will be coming to sweep them up. We have been here before. In January last year, Ankara annexed Afrin, formerly controlled by the SDF, and oversaw the ethnic cleansing of Kurdish citizens who had lived there for centuries. Turkey is allied in Syria to jihadi groups who murdered and disappeared political opposition in the city.

Turkey’s track record of using jihadists to further its policies in Syria calls into question whether the 8,000 Islamic State fighters now being held in the Autonomous Administration of NES could find themselves in Athens or London, or be used as a bargaining chip against British interests.

I went to a camp where many of these dangerous men are held. They include hundreds of Turks, thousands of Europeans, including British jihadists famed for broadcasting their beheadings of aid workers. The world cannot create a situation where these men go free.

A Turkish invasion would inexorably lead to a response by the well-trained Syrian Defence Forces, which could could drag Britain into a perverse war against its own allies in Syria to protect a NATO member.

Such an invasion would constitute a gross betrayal of our most reliable allies in the region and risks prolonging the suffering of millions of Syrians for years to come. Our engagement in the region cannot be simply about defeating ISIS, it must also be about defending those like the SDF who promote democracy and gender equality.

Britain cannot stand by and watch disaster unfold. We should suspend security and intelligence cooperation with Turkey, so that they can’t use our intelligence against one of our allies. We should bolster support for the Syrian Democratic Forces to ensure that they have the resources they need for self-defence.

Britain must stand steadfastly against the anticipated Turkish invasion – and we must use our positions in NATO, at the UN Security Council and as a member of the international coalition against Islamic State to ensure it does not happen.