By Sherine Tadros, Middle East Correspondent
For tens of thousands of Syrians, the Kilis border crossing is the official way in and out of Turkey from Syria.
But if you're an Islamic State fighter, Kilis is not an option.
Abu Mustafa (not his real name) is a Syrian people smuggler. He says he's helped hundreds of IS fighters get into Syria.
He's also brought militants - some of them injured - back out.
He took us to the spot where the smuggling happens several times a day, he says, and it didn't take long to see it in action.
We waited on the side of the road barely 10 minutes before we saw a white car speed across the open field towards the border.The Kilis border crossing is the official way into Syria from Turkey
The car stopped halfway there and six men got out each holding a big bag. The car sped off and the men headed towards the fence.
We couldn't tell if they were fighters or Syrians without passports, but they were illegally crossing into Syria.
Moments later, more people appeared at the border. It looked like a family including a woman and child.
This time the military police saw them and chased one man, possibly the smuggler, along the fence.
And the reward for taking such a risk? Abu Mustafa charges just £15 per fighter.
He said: "Last time they caught three people there were seven in total trying to get across among them Turks and Arabs.A people smuggler talks to Sky's Sherine Tadros
"But the three that got caught were foreigners. They spoke English and the police took them away.
"They often cross with their families - their wives and children. They tell us we're coming to fight with Islamic State and live there.
"Some of them don't even know where exactly they're going, they just say, we are going to the Islamic State."
It's a common story. Abu Ahmed fought with IS for 10 months in northwestern Syria.
We met him in Turkey where he agreed to speak with us as long as we covered his face and changed his name.
He joined IS at the start because they were the most effective force fighting Syrian President Bashar al Assad.
But when they turned against the Free Syrian Army (FSA) he left the group.
He explained why so many foreign fighters join the group.
"They go to Syria to be martyred, they say their former lives are over and there is no going back. Most of them rip up and throw away their passports when they arrive."
Abu Ahmed also thinks US-led airstrikes against IS are backfiring, bringing extremist groups closer together.
"After the recent strikes, more fighters are joining IS - like the Nusra Front. I know some of them who have joined," he said.
Abu Ahmed doesn't have much hope for Syria's future, or his own.
He thinks the situation is out of hand and too many players have a vested interest in keeping the war going.
"What will happen next?" he said. "Only God knows."