Image caption Jim and "Maisa", British volunteers with the Kurdish People's Protection Unit

Syria's Kurds are engaged in a bitter battle with the forces of Islamic State (IS) in the north of their country - and increasingly foreign volunteers are finding themselves on the front lines.

"Can you not show my face," the young man asked, as we stood in the Kurdish hospital in Syria. "I don't want my mum knowing I've been shot."

I'll call him Sam. He's from the south of England and is in his early 20s. He's short and slight. Standing in his camouflage gear and boots, he came up to my shoulder. With blue eyes and sallow skin, he looked 16.

Sam had been shot in the arm, in a firefight with the Islamic State.

There's been fierce fighting in north-eastern Syria as the Kurdish People's Protection Unit, or YPG, attempt to hold on to territory they've taken from the Islamic State.

The YPG have made gains - most spectacularly, with the help of coalition airstrikes, in Kobane - but on the ground they are often outgunned and outmanned by the militants.

So foreign volunteers, some of them terribly inexperienced, have been pushed from the rear, to the front. Sam included.

"It's only a flesh wound, it wasn't a sniper," he said with a giggle.

I wasn't laughing. If it had been a sniper - and IS has plenty of them, all crack shots - then Sam wouldn't be standing in front of me. Most likely, it was a stray round from an AK47.

Back home he had a desk job. Here in Syria, one of the deadliest places on earth for foreigners, he was now facing some of the most vicious and capable fighters in the Middle East.

He was woefully underequipped in every sense. The YPG has a boot camp, which lasts only a week and a half, and much of that is given over to lessons about Kurdish nationalism. There's barely time to learn the rudiments of first aid, never mind the basics of combat.

The horrors of IS war crimes had brought him here. His presence alone was itself a statement of solidarity with the Kurds and one which he hoped would bring attention to their cause, he explained.

But yet, here he was, with a bullet wound to the arm, unable to show his face because his parents didn't know just how close to death their son had come.

And he would be back on the front lines soon, he told me.

"Good luck," I said, as we left.

"Go home," was what I was thinking.

Men who take themselves to the front lines of other people's wars, are propelled by different motivations.

Image copyright Other Image caption The first Briton to die fighting with the YPG, Erik Scurfield (right), with "Peter", a US Marine

But all those I met in Syria shared a revulsion at horrors committed by the Islamic State.

Jim had been a British soldier, then a teacher in London, before he left to join the fight.

"The particular thing that brought me here was seeing a photo of an ISIS fighter holding up the severed head of a woman, and grinning at the camera," he said.

"On seeing that, although I didn't realise at the time that it was possible to come here and make a contribution, I felt I had to."

Media playback is unsupported on your device Media caption Jim, an ex-British soldier fighting IS: 'Make it possible for people to come here and fight'

Another British fighter, Maisa, was about to start a new job with a large bank. A currency trader, he had grown frustrated sitting at his desk, watching the largely unchecked rise and spread of the Islamic State.

Before he arrived in December he'd never fought in battle, though he had a background in the Territorial Army. He said he had been trained by the men he was fighting alongside, including US Rangers, and members of the French Foreign Legion.

"Obviously there is an element of throwing yourself into the deep-end," he said.

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Both men had fought alongside Erik "Konstandinos" Scurfield, a former Marine, who became the first Briton to die fighting against Islamic State in Syria at the beginning of the month.

Another common feeling among the foreign fighters is frustration, bordering on anger, that their own governments are not doing more.

"I love my country," said Peter, a former US Marine, "but if you don't cut the head of the snake here - when I say here, I mean Western Iraq, Northern Syria, spreading into Jordan and Lebanon - if you don't stop it here, if you don't fight it hard here it's coming soon to a mosque near you, any country in the world."

I met him, in Tell Brak - a town which only five days earlier had been in IS hands.

The shops had been abandoned, IS graffiti was everywhere, and of course, all the civilians had fled. The fighting in Tell Brak had been light, said Peter, but parts of the town were in ruins.

A sign near the entrance said: "Islamic Caliphacy, for the sake of Allah, is better than the democracy of the West."

Another sign left by al-Qaeda affiliate Jabat El Nusra showed a cartoon of a woman in a hijab. "The hijab will save you from hell," it said.

The Kurdish woman fighters, bareheaded and smiling, had painted a red cross through it.

If you can describe a marine as soldierly, then Peter was exactly that. The kind of guy you want at your side in a firefight. He was part of a YPG attack unit - the only foreigner among the group. In four months his Kurdish had become fluent.

The fighting, he said, had not been quite hand-to-hand, but it had been close, 5m apart in some cases.

"We'd be tossing grenades over berms, and shooting around walls," he said.

Like many of the foreigners with the Kurds, he wouldn't discuss his past, but he was concerned about his future.

Media playback is unsupported on your device Media caption A former US Marine, known as Peter: "I need to know I'm doing something good for the world"

Western governments make little distinction between those fighting for IS and those fighting against it. Bearing arms in another country's war is viewed suspiciously.

One fighter Peter knew had been questioned by six agents, two of them from the FBI, on his return to the United States. "If I ever go back I'll spend my life on a watch-list, they'll listen to my phone calls," he said.

The truth may not be as stark as that. Returning British fighters have been questioned and let go. Governments, fearful of more kidnappings and beheadings by IS, want to discourage people from travelling to Syria and Iraq.

The Syrian Kurds though, are desperate. They barely have resupply lines, beyond the weapons and ammo they take from dead IS fighters.

So for now, they will continue to welcome veterans like Peter and novices like Sam. They have no choice - they need all the help they can get.

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