Moataz lay in his hospital bed with parts of his body swathed in bandages, the victim of an artillery round by the forces of the Assad regime. He was, he said, a village teacher, adding a little later that he was also an activist, and, later still, that he was a fighter with the Free Syrian Army.

A photograph taken of him by a nurse when he first arrived for treatment a month ago showed a young man with a huge bushy beard and a wild mop of hair, the look sported by many members of Jabhat al-Nusra, an al-Qaeda affiliate vying in extremism and barbarity with Isis in the vicious civil war.

Jabhat al-Nusra has become increasingly busy around Syria’s Quneitra Governorate. Moataz was a few miles away at the Ziv Medical Centre, in Safed, one of four Israeli hospitals which have provided treatment for more than a thousand people who have suffered from violence across the border.

Many of those wounded are children and women. But men make up the bulk of the patients and the rising trend has been among those of fighting age. The volume is going up as the regime and the rebels carry out an increasingly fierce struggle for the Quneitra Passage, a route of strategic importance, with Damascus just over 40 miles away.

Also making its presence increasingly felt is Jabhat al-Nusra, arriving here after being driven out of parts of northern Syria by Isis which, in turn, has been pushed out of some of the areas it held by US-led air strikes. The opposing side, meanwhile, has been backed by large numbers of Hezbollah fighters, the Lebanese Shia militia allied to President Bashar al-Assad.

This forms an incendiary cocktail of Islamist enemies for the Jewish state. Benjamin Netanyahu’s government, which has just won a surprising and decisive victory in the national election by focusing on the security fears, claims to be neutral between the Sunni and Shia opponents, deploring, it says, any outside intervention in Syria’s internal affairs.

But the possibility of Israel being drawn into the strife has risen with the conflict expanding just a few miles away. General Mohammed Ali Allah Dadi, of the Iranian Revolutionary Guard, was reported to have been killed by an Israeli air strike in January. Jihad Mughniyeh, heading the Hezbollah forces in the Golan Heights, died alongside him. His father, Imad, was assassinated in 2008, with Mossad the chief suspect. A Syrian warplane was shot down with Damascus blaming the Israelis.

Missiles have been fired from regime-held areas into Israel. There would be fierce reprisals, say officials in Tel Aviv, if there are large scale casualties. Mount Hermon, attracting thousands of visitors with its skiing slopes, is a vulnerable potential target.

General Rami al-Hassan of the Syrian army claimed: “The first instance of co-operation between the Israeli army and al-Nusra has taken place in Quneitra where al-Nusra took the border crossing, and Israel provided them with cover under pretext of ‘shooting back’, hindering the Syrian Air Force and bringing down one of our planes.”

President Assad declared in an interview: “How can you say al-Qaeda doesn’t have an air force? They have the Israeli air force”.

The fighters in the Israeli hospitals are all from the rebel side. The Israeli military have an official policy of not commenting on how the transportation of the wounded takes place. The army medics at a field hospital, often the first point of aid, say they do not try to ascertain the allegiance of the young men.

“I don’t know and I don’t really care, my job is to help anyone who arrives here injured”, stressed a 19-year-old soldier. “I don’t ask questions, we treat everyone who comes; my family is part-Arab, I speak Arabic and that obviously helps with communications. It’s very hard when you have to deal with children, I sometimes tell the mothers to look away. But it’s also great when it goes well and you have helped them. They are very grateful, it’s nice to have their thanks.”

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Among the Syrian patients at Ziv were two women. They were from the same village near Deira, but met each other for the first time in Israel. Um-Musab has lost an eye to shrapnel, two of her sons had died in bombings. She was brought to Israel by her relations after the Jordanians refused entry. Khadija has lost both her legs in an explosion. “I was unconscious and then I found myself here. I have no contact with my family.”

Professor Anthony Luder, a gynaecologist at the Ziv, said: “This all started when an army ambulance suddenly came with patients from Syria, it has continued ever since. Our staff have a varied background and some of them speak Arabic. Everyone is doing their utmost to help; we have also had great support from the public, people sending in toys, clothes. Are some of the men fighters? Probably, but I don’t know their backgrounds. No one is ever turned away.

“These people have been brought up to believe that Israelis have horns and tails and drink children’s blood. Some of them in the past would no doubt have cut our throats under other circumstances. They come here and see what we are doing for our natural enemies.”

An Israeli soldier guards two wards where half a dozen Syrian men are treated, but the atmosphere is relaxed. One patient, Najem, 35, bemoaned the fate of his country. “The protests started off against corruption and conditions in prisons, no one thought it was going to go on for so long, now so much is destroyed.”