Turkey’s international airports have also been busy. Many, if not most, of the estimated 15,000-20,000 foreign fighters to have joined the Islamic State (Isis) have first flown into Istanbul or Adana, or arrived by ferry along its Mediterranean coast.

The influx has offered fertile ground to allies of Assad who, well before a Turkish jet shot down a Russian fighter on Tuesday, had enabled, or even supported Isis. Vladimir Putin’s reference to Turkey as “accomplices of terrorists” is likely to resonate even among some of Ankara’s backers.

From midway through 2012, when jihadis started to travel to Syria, their presence was apparent at all points of the journey to the border.

At Istanbul airport, in the southern cities of Hatay and Gaziantep – both of which were staging points – and in the border villages.

Foreigners on their way to fight remained fixtures on these routes until late in 2014 when, after continued pressure from the EU states and the US, coordinated efforts were made to turn them back.

