The Mirror's defence and security editor Chris Hughes visited the area three years ago and explains how and why security forces frequently allowed jihadists into Syria and how it lead to the Istanbul airport attack.
After days on Turkey’s border with Syria we had met every kind of jihadist - from al-Qaeda to western-friendly anti-Assad forces to Islamic State recruits.
Several times myself and photographer Adam Sorensen fled after noticing a change in the atmosphere. But mostly the fighters wanted to talk.
But a chilling incident showed how even then, in a Turkish border town called Akcakale, less than an hour from ISIS HQ Raqqa, Turkey had its eye off the ball.
Their counter-terror spooks sat in on our interviews, grinning and flashing ID cards, whispering “secret police” as they joined us in cafes.
Three times a day Turkish tanks guarding the border would pull to one side and fighters poured into Turkey for supplies under the approving eye of the Turkish police and Army.
The police had no problem with the fighters, as long as they were causing mayhem for Syria’s regime - and as long as they were not Kurds.
Whoever they fought for, the Syrian jihadists enjoyed status in southern Turkey - but when we tried to interview ordinary Kurds it was a different story.
After talking to a Kurdish family living nearby, our car was stopped at gunpoint and five plain-clothes Turkish cops dragged us into the street.
We were searched and arrested at gunpoint and they demanded to know why we had been meeting Kurds.
We told them we had been in the area for a week, talking to everyone including refugees and fighters until finally a few hours later we were released from the local police station.
That was three years ago and ISIS was burgeoning whilst the Kurds were the threat being taken most seriously on the border.
Turkey’s security forces and intelligence agencies have for too long had a duplicitous view towards jihadists - approving of the mayhem they caused in neighbouring Syria, whilst neglecting the threat they posed.
And at the same time the Turkish regime has brutally cracked down on the very Kurdish opposition that has helped fight Islamic State.
Turkey has failed to adapt to an ever-changing situation and is suffering from failing to plug its border and crack down on the jihadists from Syria whilst concentrating on Kurdish opposition.