In the face of stinging criticism at home and concerns abroad, United States President Donald Trump has demanded a ceasefire, imposed tariffs on Turkish steel and threatened more sanctions over Ankara's incursions into north-eastern Syria - just over a week after virtually green-lighting the military move. Some of the strongest words came from Republican lawmaker Lindsey Graham, a staunch Trump supporter, who called Mr Trump "short-sighted and irresponsible". Mr Trump's earlier announcement to remove US troops stationed in the area in the face of planned Turkish military action against Kurdish forces there engendered unsettling consequences for an already volatile Middle East region. His decision effectively gave Ankara the go-ahead to attack the Kurds, who have been key US allies in the fight to defeat the Islamic State in Iraq and Syria (ISIS) terrorist group.

ISIS no longer holds territory in the area, unlike some years ago. But tens of thousands of ISIS fighters, their families and supporters are on the ground in Syria and Iraq. Several thousand fighters, many of them foreigners, are in prisons in north-east Syria; tens of thousands who lived in ISIS-controlled areas, including ISIS sympathisers, remain in camps. With Turkish and Kurdish forces facing off, remnant ISIS fighters will see the opportunity to regroup. Others could seize the chance to flee and make their way across to Europe or South-east Asia and cause mayhem. There are reports that hundreds of ISIS supporters have escaped, and are linking up. In the wake of Mr Trump's decision, governments in the region and beyond must brace themselves for what may come should ISIS fighters cross into their borders. Former US defence secretary James Mattis has said in no uncertain terms that unless pressure is kept on ISIS, it will resurge.