The patient started screaming, convulsed with pain, when the last painkillers were used up in the dark cellar. "We continued with the surgery nonetheless," Omar says in a quiet voice. "We had no choice. He would have bled to death if we hadn't." The man's stomach had been torn open by shell splinters. His screams still echo in Omar's nightmares – even months after Omar returned from Syria to Germany.

Omar is not his real name. The Syrian surgeon works in a clinic in a city in Germany whose name he wants to be kept secret. The man who calls himself Omar fears for his parents and siblings in Aleppo. Nobody must know that in one cold night a few months ago, he sneaked across the Turkish-Syrian border into Syria – following a call on Facebook by people in a small village in Northern Syria's mountains, who were desperately looking for an experienced surgeon. Omar received support from doctor friends of his, Syrians living in Germany or France, who have set up an informal network. Together, they collected medicine and medical instruments and took them across the border themselves – defying the danger.

"Hospitals are attacked specifically"

Omar is certain that his family would have been in grave danger if anybody had found out that he treated patients for a week in different cellars and bombed-out houses. A few weeks ago, a general practitioner was killed in Aleppo. He had been a good friend of Omar's from school. "A couple of policemen came into his practice and simply shot him dead," Omar says. His friend had refused to continue collaborating with the security forces in Aleppo – the next day he was dead.

"In Syria, hospitals and ambulances are attacked specifically," confirms Tankred Stöbe, chairman of the German branch of Doctors Without Borders. Almost 60 percent of hospitals and 80 percent of ambulances have been damaged in the fights between rebels and the Syrian army, Stöbe estimates. "That shows that it's not a random phenomenon. They're targeted specifically," he says.

Doctors Without Borders says it runs five emergency clinics in Syria. They're all located in villages and towns controlled by the rebels. "The regime denies us access to their areas," says Stöbe, adding that at the end of last year he helped set up one such clinic in a small mountain grotto in Syria. But he won't tell us the exact location of the cave – because of "security concerns". The entire region, he adds, "is practically under constant fire". Which means that the clinic run by the international aid organization could also become an easy target.

"People bleeding to death"

Stöbe's team had to carry all the equipment for the small clinic secretly across the border from Turkey at night – via different transport routes. "Everything, from operating tables and first aid equipment to medicine." Syrian medicine production has come to a standstill. There is a lack of medicine and dressing material, and many doctors and nurses have long since fled the fighting that has been going on for two years now.

Many children are not vaccinated any more. "I've heard dozens of stories about people who have bled to death just because there was nobody to help them." War injuries, such as severe shell and bullet wounds, need to be treated immediately, the doctor from Berlin says. "You call it the golden hour – if you don't operate within the first hour and stop the bleeding, it's too late."

The patients come to Stöbe's clinic at night. Some arrive on small trucks whose lights are shaded, others walk on foot. The transport system in northern Syria is completely dysfunctional. There are no more vehicles on the highways. Streets are filled with landmines and many roads have been badly damaged from artillery shelling and bombings. Bigger towns often cannot be reached because of blockades and checkpoints. "The border lines change from one day to the next, often even from one hour to the next." Villages are sometimes cut off overnight.

For many people, the small and improvised village clinics in bombed out or hidden houses are frequently the only access to medical treatment they have. "Clinic is the wrong word really. It was just one room in a cellar," says Omar, adding that the electricity supply was often disrupted and operations were conducted by torchlight.

Blood vessels blocked with hairpins

Omar would work together with first-year students of medicine and nurses – people who were overwhelmed by all the patients that would flood the improvised clinic in the cellar day after day.

"Every night, we had new wounded to treat," Omar recalls. Among them, were people who had been wounded in bomb attacks, pregnant women, patients with asthma and other chronic diseases who couldn't get hold of the medicine they needed.

After only a few days, all the medicine he had bought in Turkey was used up. "We had hardly any medical instruments at all. We would heat up the dressing material in the oven to make it as sterile as possible," he says, adding that that was, of course, completely insufficient. "But what were we supposed to do?" Omar would often have to block blood vessels with hairpins to stop the bleeding. "I should register the method as my own patent." Omar laughs, but it's a desperate laugh – almost hysterical.

He was completely unaware of what was waiting for him in Syria when he went there, he says. "I had no idea it would be so terrible and that I would see so many horrible things." After one week in Syria, he learned of a bomb attack on a neighboring village. He went there instantly together with a few colleagues. "I got out of the vehicle, went into one bombed-out house from which I could hear people screaming. And then, the pick-up was bombed."

Omar pauses for a brief moment, takes a few deep breaths, swallows, and continues. He ran back to the pick-up immediately, "but there was nothing there any more: the pick-up, my friends, everything was gone. There were body parts scattered all over the place." His voice becomes quiet when he adds that he escaped death by a mere twenty seconds. The following day, he traveled back to Turkey and on to Germany. "That was it for me."

"As if I killed those people"

"Tonight will probably be another sleepless night for me," says Omar at the end of the conversation. He will see the face of a six-year-old girl again whose leg he had to amputate because he was lacking the specialized tools to save it. He will again hear the screams of the man who was operated on without any painkillers. And he will ask himself again whether he should travel to Syria to save people's lives. He has one week of holidays coming up this summer. His boss left a handwritten note on his vacation form, which read: "Only valid in Germany", Omar says. "It was a joke of course. But he doesn't want me to go back to Syria." Omar says his wife has been crying for weeks, she has begged him to stay. She urges him to think of his family, his two children and not to risk his life.

Yes, says Omar, he is terrified about going back to Syria. "But if I stay in Germany people will die who I could have saved." In a way, Omar believes he is partly responsible for their death – as if they were killed by him and not by the bombs and the shells of the civil war going on in Syria. "I have to help. I'm a doctor." Omar pauses briefly, and then adds "I hate Assad. But if he came into my clinic wounded – of course I'd help him."