A quick overview of the rise of IS

in a book review The Hijackers by Hugh Roberts:
"...US intelligence had anticipated the rise of Islamic State nearly two years before it happened. On 18 May, a document from the US Defense Intelligence Agency dated 12 August 2012 was published by a conservative watchdog organisation called Judicial Watch, which had managed to obtain this and other formerly classified documents through a federal lawsuit. The document not only anticipates the rise of IS but seems to suggest it would be a desirable development from the point of view of the international ‘coalition’ seeking regime change in Damascus...........

If Islamic State escaped whatever influence Western intelligence services may initially have sought to have on it and went its own way, this means that people have been playing with fire.

I don’t pretend to know what the truth is. But there is no need to prove malign intent on the part of the Western powers. The most charitable theory available, ‘the eternally recurring colossal cock-up’ theory of history, will do well enough. If a more sophisticated theory is required, I suggest we recall the assessment of C. Wright Mills when he spoke of US policy being made by ‘crackpot realists’, people who were entirely realistic about how to promote their careers inside the Beltway, and incorrigible crackpots when it came to formulating foreign policy. Since it is not only American folly and incompetence that is in the dock, I would also recall the assessment of Ernest Bevin, who remarked that ‘superiority is claimed by the middle class in the realms of government, when as a matter of fact their work is a monument of incompetence.’

Western policy has been a disgrace and Britain’s contribution to it should be a matter of national shame. Whatever has motivated it, it has been a disaster for Iraq, Libya and now Syria, and the fallout is killing Americans, French people and now British tourists, in addition to its uncounted victims in the Middle East. The case for changing this policy, at least where Syria is concerned, is overwhelming......

What can be done about Islamic State? As things stand, very little. As Cockburn was among the first to point out, air power will not stop it and nor will the corruption-ridden and demoralised Iraqi army; meanwhile, the much more combative but ferociously sectarian Shia militias are driving Sunni Iraqis into Islamic State’s arms. Sending in Western troops would be folly, a gift to the enemy. Training a few hundred Iraqis here or a few hundred Syrians there is obviously not a serious policy but a fatuous surrogate for one. What does this leave? The answer is that unless the Syrian army takes on Islamic State, IS will stay in business indefinitely......

But I’m not a think-tanker. And, apart from wanting an end to the war in Syria for its own sake, I want and believe that every real democrat would want Tunisia, the sole democracy in the Arab world, to be helped and defended from the depredations of all forms of terrorism. Western governments must be induced by public opinion in their own countries to drop the veto on a negotiated end to the war in Syria that the demand that Assad must go has amounted to. This stance, pre-empting the right of the Syrian people to decide the matter, has always been wrong in democratic principle and it has been catastrophic in practice. This doesn’t mean that they have to declare that Assad can stay. That too would be wrong in principle. But they could moderate their position: they could say that they believe Assad should step down before long but that they recognise it is for the Syrian people to decide. "