Isil’s lasting legacy

American-backed coalition forces have launched their final assault on Isil militants based in the city of Raqqa. While the troops are certain to encounter pockets of fierce resistance from jihadists prepared to fight to the last, the self-styled caliphate that established itself in war-torn Syria some three years ago is close to collapse. Its impending end should be a cause of celebration, and yet its baleful influence will be apparent for years to come.

Thousands of militant Islamists travelled to Raqqa, and while many were killed others have returned to their home countries where they remain a long-term threat to security. An estimated 300 British jihadists have come back to the UK after a spell in the so-called Islamic State and will have to be kept under surveillance.

But even if the efforts to establish an Islamist state have been thwarted, the ideology that underpins it is deeply rooted in the extremist Sunni networks of the Middle East. It will seek to re-emerge in ungoverned space elsewhere, such as Libya, Yemen or the Sinai. History shows that this menace is never extirpated and the West needs to prepare for the next iteration and deal with it before it grows. It cannot rely upon Sunni Middle East states to impose law and order in the region.

Meanwhile, Iranian-backed Shia militias such as Hezbollah have also been emboldened by the collapse of Isil and professionalised by the fighting. A conflict could break out at any moment between Iraqi Shia forces and Kurdish Peshmerga troops occupying Kirkuk, another legacy of the caliphate. The Kurds want their own homeland as a reward for helping to defeat the Islamists. Raqqa may fall soon. But peace is a long way off.