The combined assault drove al-Qaeda-aligned insurgents from many of their havens and inflicted on them crippling losses. But, given mounting American casualties and the refusal of most allies to do much fighting, the US eventually withdrew from what was widely perceived to be a costly, illegitimate, increasingly unpopular and ultimately unwinnable ground war.

The hope was that the emerging Iraqi state would soon acquire the political and security infrastructure to establish a relatively stable social order. This proved to be a forlorn hope.

The violence of the past three decades continues to take its toll. The Iran-Iraq war (1980-88), in which the US at different times armed both sides in its desire to prevent either side dominating the vital oil region, cost the lives of half a million Iraqi and Iranian soldiers and a similar number of civilians. Soon after came the Gulf War (1990-1991), the economic sanctions and air strikes conducted by the US through the 1990s, and the protracted conflict that followed the 2003 US invasion. Conservative estimates suggest that since then close to 150,000 civilians have been killed. Indeed, the number of those who have died directly or indirectly as a result of the war may well exceed 500,000.

This prolonged violence has meant the destruction of the economic, social and cultural fabric of the country and given rise to warring fiefdoms, sectarian hatreds and pervasive corruption. America's failure to establish the conditions for legitimate governance has in turn provided fertile ground for an array of extremist groups, each claiming to act in the name of Islam, of which to date IS is the most brutal, organisationally the most sophisticated, and militarily the most successful incarnation.

IS, which now controls a large part of the north-west of Iraq and north-east of Syria, is also the beneficiary of the West's ill-conceived attempts at regime change in Syria. Obsessed with the possible rise of Iran as a major regional power, Washington has long pursued a policy of supporting Tehran's enemies and opposing its clients and friends. Accordingly, it has sought by all possible means, except for direct military intervention, to bring about President Assad's downfall. This has necessitated funding and arming an assortment of rebel groups, and importantly turning a blind eye, at least until recently, to the competing hardline Islamist groups financially and logistically supported by Saudi Arabia and Qatar.