GETTY Ryan said a united front between Cameron, Obama, Putin and Assad is needed to defeat ISIS

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A terror expert warns the feared group can only be crushed with a unusual concerted effort between Syria, Russia and the West. Following Russia setting up an air base in Syria to help the Middle East country in its fight against ISIS, former SAS man-turned novelist Chris Ryan said now is the opportunity to crack the biggest threat to world peace. He said: "For us to get ISIS would need to have a link up with Syria and the targeting of its strongholds. All the areas along the Anbar Province - between Iraq and Syria - that's where we need to hit. "The best idea would be to hit them both sides with Europe and the United States one side and Russia on the other. "The longer we wait, the stronger ISIS will get."

GETTY Cameron said yesterday that Assad needs to be dealt with

GETTY Assad and Putin are long time allies

However, British Government policy makes such a united front unlikely. Just yesterday Prime Minister David Cameron, when signalling a push for more military action in the region, said Assad as well as ISIS should be the target of an attack. He said the Syrian leader had "butchered his own people" and called for a government which would "look after its people". But Ryan, who fought in the first Gulf War, believes he's the lesser of two evils and bringing more instability to the region by toppling Assad could be a disaster. The former British Special Forces operative and soldier said grave errors were made in the last Iraq War in taking power away from the ruling Sunnis and that ultimately created a vacuum for ISIS to breed in. He said: "One of the biggest mistakes of the second Gulf War was when we took control of the country and sacked every member of the police and army and handed it over to Shias. All the commanders and military went back to the dessert and plotted.

GETTY General Schwarzkopf defended not toppling Saddam Hussain in the first Gulf War

The longer we wait, the stronger ISIS will get Chris Ryan

"It should have been a mixture of Shias and Sunnis, bringing some stability. "I once spoke to US General Norman Schwarzkopf and asked him why we didn't take out Saddam at the end of the first war in Iraq. "He said 'if we took out the regime it would destabilise the country, the whole region'. "And now it's happened, the whole region has been destabilised and everything he said has come true." Ryan believes a ground invasion of ISIS areas must also be seriously looked at, however, that would come with a diplomatic nightmare. He said: "We would need help from Saudi Arabia and other neighbouring countries. "But the thing with Sunnis and Shias divides getting people to sing from the same hymn sheet is very difficult."

Former SAS man Chris Ryan has experience of both Syria and Iraq [NIALLMCDIARMID]