Islamic State (Isis) forces in Syria are threatening to capture a crucial road, the loss of which could touch off a panic and the exodus of several million refugees from government areas, in addition to the four million who have already fled. Isis fighters have advanced recently to within 22 miles of the M5 highway, the only major route connecting government-held territory in Damascus to the north and west of the country.

The beginnings of the latest crisis for the government of President Bashar al-Assad came with the capture by Isis on 6 August of the strategically placed, largely Christian town of al-Qaryatain, north-east of Damascus. Since then, Islamist units have advanced further west, capturing two villages closer to the M5. The Syrian Army has so far failed to retake Qaryatain, where Isis has demolished the St Elian monastery, parts of which were 1,500 years old.

The four million Syrians who are already refugees mostly came from opposition or contested areas that have been systematically bombarded by government aircraft and artillery, making them uninhabitable. But the majority of the 17 million Syrians still in the country live in government-controlled areas now threatened by Isis. These people are terrified of Isis occupying their cities, towns and villages because of its reputation for mass executions, ritual mutilation and rape against those not obedient to its extreme variant of Sunni Islam.

Half the Syrian population has already been displaced inside or outside the country, so accurate figures are hard to estimate, but among those particularly at risk are the Alawites (2.6 million), the Shia heterodox sect that has provided the ruling elite of Syria since the 1960s, the Christians (two million), the Syrian Kurds (2.2 million), and Druze (650,000) in addition to millions of Sunni Arabs associated with the Syrian government and its army. The forced flight of these communities could swiftly double the total number of refugees to eight million.

Government forces are showing signs of being fought out after four years of war and have recently suffered a series of defeats at the hands of Isis, which captured Palmyra in May, and by a coalition led by the al-Qaeda affiliate, Jabhat al-Nusra, which took Idlib city in March. But it would be a far more serious defeat for President Assad if Isis cuts the M5, which is seen as “the spinal column of the regime”. The government has never lost control of it for an extended period, though the road has been closed to civilian traffic by snipers hiding in the ruins of north Damascus, where whole districts have been blown up or bulldozed by the government. On two occasions, Nusra fighters seized the ancient Christian village of Maaloula, just off the M5, forcing inhabitants to escape to Damascus.

Governments and people in the EU have had to pay horrified attention to the plight of refugees in the past few days because of pictures of the drowned body of Aylan al-Kurdi. But there is scant attention to the deteriorating security situation in Syria that could produce millions more migrants fleeing for their lives.

The UNHCR says that Syria has “become the world’s top source country of refugees, overtaking Afghanistan, which had held this position for more than three decades”. Out of every four new refugees in the world today, one will be a Syrian. Commenting on this exodus, and the likelihood that it will be exacerbated if Isis cuts the M5 highway, the online humanitarian news and analysis publication, IRIN, says that “Europe’s current migration crisis is essentially the arrival of the Syrian crisis on European shores.”

Unfortunately, European concern about ending the refugee crisis has not energised efforts to end the war in Syria which shows every sign of getting worse. Assad’s forces are getting weaker and he admits to a shortage of troops, but territory lost by him is usually occupied by Isis, Jabhat al-Nusra or Ahrar al-Sham, all Salafi-jihadi movements with the same violent and intolerant ideology.

Even former advocates of the “moderate” Syrian rebels, say that today the armed opposition is dominated by extreme fundamentalists. Their dominance makes it impossible to create any power-sharing government in Damascus that would be key to ending the war.

The Damascus government and its army are unlikely to implode as happened in Libya or northern Iraq, but people in government areas are understandably frightened by recent military reverses. Many argue that they and their families should get out while they can. Living in government areas does not always mean that they are in favour of Assad remaining in power, but they fear that the alternative to the present regime will be far worse. Isis deliberately foments terror by showing videos of its atrocities to create panic among soldiers and civilians, and there is also the knowledge that the Syrian Army will bombard any place from which it retreats.

The refugee crisis - in pictures Show all 70 1 /70 The refugee crisis - in pictures The refugee crisis - in pictures Refugees fleeing conflict A Syrian refugee holding a baby in a lifetube swims towards the shore after their dinghy deflated some 100m away before reaching the Greek island of Lesbos The refugee crisis - in pictures Refugees fleeing conflict A refugee raises a child into the air as Syrian and Afghan refugees are seen on and around a dinghy that deflated some 100m away before reaching the Greek island of Lesbos The refugee crisis - in pictures Refugees fleeing conflict Syrian and Afghan refugees fall into the sea after their dinghy deflated some 100m away before reaching the Greek island of Lesbos The refugee crisis - in pictures Refugees fleeing conflict A refugee cries as he holds a child on the Serbian side of the border with Hungary in Asotthalom Reuters The refugee crisis - in pictures Refugees fleeing conflict Refugees stand in front of a barrier at the border with Hungary near the village of Horgos, Serbia Reuters The refugee crisis - in pictures Refugees fleeing conflict A refugee from Syria prays after arriving on the shores of the Greek island of Lesbos aboard an inflatable dinghy across the Aegean Sea from from Turkey. Greece sent troops and police reinforcements to Lesbos after renewed clashes between police and migrants, the public broadcaster said, while Syrian refugees on the island were targeted with Molotov cocktail attacks The refugee crisis - in pictures Refugees fleeing conflict Police try to stop refugees going under a fence to board a train at a station near Gevgelija, Macedonia. Several thousand refugees in Macedonia boarded trains to travel north after spending a night in a provisional camp. Macedonia has organised trains twice a day to the north border where they cross into Serbia to make their way to Hungary The refugee crisis - in pictures Refugees fleeing conflict Refugees push each other as they try to board a bus following their arrival onboard the Eleftherios Venizelos passenger ship at the port of Piraeus, near Athens, Greece The refugee crisis - in pictures Refugees fleeing conflict Refugees are welcomed by locals after their arrival at the main railway station in Frankfurt, Germany. Over 1,000 more refugees arrived in Germany to cheers and "welcome" signs, but calls grew for a European solution to its worst refugee crisis since World War II The refugee crisis - in pictures Refugees fleeing conflict A young Syrian boy arrives on the Greek island of Lesbos after crossing in a dinghy with other refugees from Turkey AP The refugee crisis - in pictures Refugees fleeing conflict Refugees walk on the railway tracks between Bicske and Szar, some 40 kms west of Budapest, trying to reach Germany EPA The refugee crisis - in pictures Refugees fleeing conflict Hungarian policemen stand by the family of refugees as they wanted to run away at the railway station in the town of Bicske, Hungary The refugee crisis - in pictures Refugees fleeing conflict A family is arrested by local police after their local train coming from Budapest and heading to the Austrian border has been stopped in Bicske, west of the Hungarian capital The refugee crisis - in pictures Refugees fleeing conflict A man is arrested by local police after his local train coming from Budapest and heading to the Austrian border has been stopped in Bicske, west of the Hungarian capital The refugee crisis - in pictures Refugees fleeing conflict More than 2,500 refugees have died trying to reach Europe this year and the struggle continues as they travel through the continent Getty Images The refugee crisis - in pictures Refugees fleeing conflict Refugees protest in front of a train at Bicske railway station. Hundreds of people, were stranded on a train in Hungary for a second, demanding passage to Germany in a standoff with riot police The refugee crisis - in pictures Refugees fleeing conflict Syrian refugees arrive on the shores of Lesvos island Getty The refugee crisis - in pictures Refugees fleeing conflict Syrian refugees on the Greek Macedonian border Getty The refugee crisis - in pictures Refugees fleeing conflict Refugees storm into a train at the Keleti train station as Hungarian police withdrew from the gates after two days of blocking their entry The refugee crisis - in pictures Refugees fleeing conflict Refugees storm into a train at the Keleti train station in Budapest The refugee crisis - in pictures Refugees fleeing conflict Refugees cross the border between the Former Yugoslav Republic of Macedonia and Greece, near the town of Gevgelija, Macedonia. The Gevgelija-Presevo journey is just a part of the journey that the refugees, the vast majority of them from Syria, are forced to make along the so-called Balkan corridor, which takes them from Turkey, across Greece, Macedonia and Serbia to Hungary, the gateway to the European Union, September 2015 The refugee crisis - in pictures Refugees fleeing conflict A refugee helps up an exhausted fellow refugee as they cross the border between Macedonia and Greece, near the town of Gevgelija, September 2015 The refugee crisis - in pictures Refugees fleeing conflict People breaking through a police cordon and crossing the border between Macedonia and Greece, September 2015 The refugee crisis - in pictures Refugees fleeing conflict Refugees pass the border between Macedonia and Greece, September 2015 The refugee crisis - in pictures Refugees fleeing conflict A Macedonian policeman carries a child across the border between Macedonia and Greece, September 2015 The refugee crisis - in pictures Refugees fleeing conflict Syrians sleep on railroad tracks waiting to be processed across the Macedonian border in Idomeni, Greece, September 2015 The refugee crisis - in pictures Refugees fleeing conflict A Czech police officer marks a refugee with a number after more than than 200 refugees were detained, mostly from Syria, on trains from Hungary and Austria at the railway station in Breclav, Czech Republic, September 2015 AP Photo, CTK/Igor Zehl The refugee crisis - in pictures Refugees fleeing conflict A baby is lifted on to the Norwegian vessel ‘Siem Pilot’ during a search-and-rescue mission off the Libyan coast, September 2015 AP The refugee crisis - in pictures Refugees fleeing conflict Budapest's main international railway station ordered an evacuation as hundreds of people tried to board trains to Austria and Germany, September 2015 The refugee crisis - in pictures Refugees fleeing conflict People wave their train tickets and lift up children outside the main Eastern Railway station in Budapest, September 2015 The refugee crisis - in pictures Refugees fleeing conflict People protest at the Eastern (Keleti) railway station of Budapest, September 2015 The refugee crisis - in pictures Refugees fleeing conflict Refugee children sleep in the surrounding green area of the Keleti railway station in Budapest, September 2015 The refugee crisis - in pictures Refugees fleeing conflict Syrians cross under a fence into Hungary at the border with Serbia, near Roszke, August 2015 Reuters The refugee crisis - in pictures Refugees fleeing conflict Refugees who have just crossed the border from Serbia into Hungary walk along a railway track that joins the two countries, August 2015 Getty Images The refugee crisis - in pictures Refugees fleeing conflict Police arrest refugees at Cobham Services on the M25 in Surrey, August 2015 Twitter: @bigwheeluk The refugee crisis - in pictures Refugees fleeing conflict Men hold a boy as they are stuck between Macedonian riot police officers and fellow refugees during a clash near the border train station of Idomeni, August 2015 AFP/Getty The refugee crisis - in pictures Refugees fleeing conflict A Syrian father holds his children close as his arrives on the Greek Island of Kos, August 2015 Eyevine The refugee crisis - in pictures Refugees fleeing conflict A tourist offers water to Iranian refugees as they arrive by paddling an engineless dinghy from the Turkish coast (seen in the background) at a beach on the Greek island of Kos, August 2015 Reuters The refugee crisis - in pictures Refugees fleeing conflict A Syrian holds his 30-day-old baby on an overcrowded train as they travel through Macedonia. Tens of thousands of refugees, mainly from the Middle East and Africa, use the Balkans route to get into the European Union, passing from Greece to Macedonia and Serbia and then to western Europe, August 2015 The refugee crisis - in pictures Refugees fleeing conflict A man rests on a platform at the train station in Gevgelija, on the Macedonian-Greek border, August 2015 Getty The refugee crisis - in pictures Refugees fleeing conflict Refugees react after boarding the Migrant Offshore Aid Station (MOAS) ship MV Phoenix some 20 miles (32 kilometres) off the coast of Libya. Some 118 refugees were rescued from a rubber dinghy off Libya. The Phoenix, manned by personnel from international non-governmental organisations Medecins san Frontiere (MSF) and MOAS, is the first privately funded vessel to operate in the Mediterranean, August 2015 The refugee crisis - in pictures Refugees fleeing conflict Authorities are being overwhelmed as they try to fight off hundreds of refugees, prompting France to beef up its police presence, July 2015 AFP The refugee crisis - in pictures Refugees fleeing conflict People escape from the French Police as they try to catch a train to reach England, July 2015 EPA The refugee crisis - in pictures Refugees fleeing conflict A man jumps over a fence as he attempts to access the Channel Tunnel, in Calais, northern France, July 2015 PA/Thibault Camus The refugee crisis - in pictures Refugees fleeing conflict Two men cling to the roof of a freight truck as it leaves the Eurotunnel terminal in Folkestone, July 2015 Getty The refugee crisis - in pictures Refugees fleeing conflict A man climbs a security fence of a Eurotunnel terminal in Coquelles near Calais, July 2015 The refugee crisis - in pictures Refugees fleeing conflict Men help a man squeeze through a gap in a fence near the Eurotunnel terminal in Coquelles in Calais, July 2015 Getty The refugee crisis - in pictures Refugees fleeing conflict Desperate for entry to the EU, the group of people risked being washed away by the sea at Ventimiglia rocks, June 2015 The refugee crisis - in pictures Refugees fleeing conflict Stranded refugees spend night on rocks - they were supplied with emergency blankets after a cold night next to the sea, June 2015 The refugee crisis - in pictures Refugees fleeing conflict Refugees climb in the back of a lorry on the A16 highway leading to the Eurotunnel in Calais, June 2015 Getty Images The refugee crisis - in pictures Refugees fleeing conflict A police officer sprays tear gas to men trying to access the Channel Tunnel on the A16 highway in Calais, northern France, June 2015 PHILIPPE HUGUEN/AFP/Getty Images The refugee crisis - in pictures Refugees fleeing conflict Men jump out of a lorry after being discovered by French gendarmerie officers, June 2015 AP The refugee crisis - in pictures Refugees fleeing conflict A man sits under the trailer of a lorry, June 2015 AP The refugee crisis - in pictures Refugees fleeing conflict A Belgian navy sailor passes life vests to refugees sitting in a rubber boat as they approach the Belgian Navy Vessel Godetia, June 2015 AP The refugee crisis - in pictures Refugees fleeing conflict People on the Belgian Navy vessel Godetia after they were saved during a search and rescue mission in the Mediterranean off the Libyan coast, June 2015 AP The refugee crisis - in pictures Refugees fleeing conflict Iraqis wait as they are detained by Hungarian police after crossing the Hungarian-Serbian border illegally near the village of Asotthalom, Hungary, June 2015 Reuters The refugee crisis - in pictures Refugees fleeing conflict Syrian refugees walking on train tracks through Macedonia on the Western Balkans migration route, after entering Europe through Greece, June 2015 Reuters The refugee crisis - in pictures Refugees fleeing conflict A group of people huddle together during an operation to remove them from the Italian-French border in the Italian city of Ventimiglia. Italy and France engaged in a war of words as a standoff over hundreds of Africans offered a graphic illustration of Europe's migration crisis. Italian Interior Minister Angelino Alfano described images of refugees perched on rocks at the border town of Ventimiglia after being refused entry to France as a "punch in the face for Europe", June 2015 The refugee crisis - in pictures Refugees fleeing conflict A man is carried by Italian police in Ventimiglia, Italy. Police reportedly removed refugees from under a railway bridge, June 2015 EPA The refugee crisis - in pictures Refugees fleeing conflict People queue after disembarking from the Royal Navy ship HMS 'Bulwark' upon their arrival in the port of Catania on the coast of Sicily, June 2015 GIOVANNI ISOLINO/AFP/Getty Images The refugee crisis - in pictures Refugees fleeing conflict A Syrian child holds a drawing as he waits to disembark from Belgian Navy vessel Godetia at the Augusta port, Italy. Around 250 refugees from Syria arrived at the Sicilian harbour from a Damascus refugee camp, June 2015 The refugee crisis - in pictures Refugees fleeing conflict A dinghy overcrowded with Afghan refugees arrived on a beach on the Greek island of Kos, May 2015 The refugee crisis - in pictures Refugees fleeing conflict An Afghan child is helped off a rib on the Greek island of Kos, May 2015 The refugee crisis - in pictures Refugees fleeing conflict An Afghan girl holds the hand of a woman as they arrive on a beach on the Greek island of Kos, after crossing a part of the Aegean Sea between Turkey and Greece, May 2015 The refugee crisis - in pictures Refugees fleeing conflict Refugees crossed part of the Aegean Sea between Turkey and Greece, May 2015 The refugee crisis - in pictures Refugees fleeing conflict Afghan refugees arrive on a beach of Kos, May 2015 The refugee crisis - in pictures Refugees fleeing conflict Rescuers help children to disembark in the Sicilian harbor of Pozzallo, Italy in April 2015 The refugee crisis - in pictures Refugees fleeing conflict A boat transporting refugees arrives in the port of Messina after a rescue operation at sea, April 2015 Getty The refugee crisis - in pictures Refugees fleeing conflict Armed Forces of Malta personnel in protective clothing carry the body of a dead man off Italian coastguard ship Bruno Gregoretti as surviving refugees watch in Senglea, in Valletta's Grand Harbour, April 2015 The refugee crisis - in pictures Refugees fleeing conflict Rescued people talk to a member of the Malta Order after a fishing boat carrying refugees capsized off the Libyan coast, is brought ashore along with 23 others retreived by the Italian Coast Guard vessel Bruno Gregoretti at Boiler Wharf, Senglea in Malta, April 2015

David Cameron said last week: “We think that the most important thing is to try to bring peace and stability to that part of the world.” But in practice, Britain, the US, Gulf monarchies and Turkey have exacerbated the Syrian conflict by supporting an armed opposition that from an early stage was led by extreme jihadis. As early as August 2012 a Defense Intelligence Agency report states that “the Salafist, the Muslim Brotherhood, and AQI [Al- Qaeda in Iraq] are the major forces driving the insurgency in Syria.”

Likely British participation in the US-led air campaign against Isis in Syria will make little difference unless it is directed against Isis when it is attacking the Syrian Army and is co-ordinated with its ground forces. These tactics worked effectively when the US collaborated with the Syrian Kurdish YPG militia to win battles at Kobani and Hassakah, but the US is so far opposed to doing anything that will be seen as helping the Assad government. A price for such aid might be an insistence that the Syrian air force stop barrel bombing civilian areas.

Surprisingly, even the fall of Mosul in Iraq to Isis in the summer of 2014 and the seizure of more than half of Syria by Isis over the past year, has not prevented US and European leaders underestimating Isis. They have claimed that it is past its peak, wishful thinking that should have been deflated in May when Isis took Ramadi, the capital of Anbar province in Iraq, and Palmyra in Syria five days later. So far neither the Syrian nor the Iraqi armies have launched counter-attacks capable of retaking either city.