The major ethnic groups in Iraq are the Arabs, which constitute 75% to 80% of the population, and the Kurds, which constitute 15% to 20% of the population.
Islam is, of course, the dominant religion, with 97% of Iraqis identifying themselves as Muslims. Among the Muslims, 60%-65% are Shiites and 32% to 37% are Sunnis.
The Kurdish minority is largely Sunni, and roughly half of the Sunnis are Kurds. But the Kurds have long been very antagonistic toward the Arab majority.
So Shiite Arabs outnumber Sunni Arabs not two to one but three or even four to one.
The Shiite majority controls the major cities from Baghdad south, as well as the major oil-producing regions of the nation.
These numbers are important in considering the ISIS insurgency, which thus far has seized control of territory largely in the Sunni-dominated areas of Iraq. Notably, ISIS has not attempted to seize either Kurdish territory. Since the end of the first Gulf War in the early 1990s, the Kurdish region has been politically autonomous, and since the fall of Saddam Hussein, it has developed one of the strongest, best trained, and best equipped militaries in the region. ISIS also has not yet attacked the territories dominated by the Shiite majority, which controls the reconstituted Iraqi military and has major military support from Iran.
Even more than the former Yugoslavia, Iraq has always been a nation in which intense ethnic and religious animosities could be held in check only by authoritarian regimes all too willing to use excessive military force to suppress division as well as dissent. If Iraq splits into three nations, it will not necessarily be a disaster for anyone but the Ba’athists who now seem to have desperately allied themselves with religious extremists that even al Qaeda has denounced as too extreme. Clearly ISIS can terribly disrupt the civil order in all parts of Iraq, but, outside of its own enclaves, it does not seem any more capable than the Taliban of Afghanistan and Pakistan of ruling in any sustained and broadly supported way.
Our ten-year occupation of Iraq could not transform an inherently divided state into a unified nation. In effect, we compensated for the massacres of Kurds and Shiites that followed the first Gulf War by providing both groups with the means to defend themselves against the Sunnis. Perhaps only the passage of time will allow us to determine whether our conquest of Iraq produced anything positive or it was simply an unmitigated disaster. But, the situation in Syria demonstrates that the deep tensions within these states, most recently rather arbitrarily defined by European imperialists, may be exacerbated by our intervention or non-intervention, but we are not their primary historical cause. Indeed, the largest Kurdish population anywhere is in Turkey, which has been treating their desire for autonomy as an insurgency since Turkey formed out of the core remnants of the Ottoman Empire. Even in Iran, which is viewed as demographically and politically homogenous by most in the West, Turkic, Kurdish, and other minorities constitute a third of the population.
Map from Brandon Christensen’s “The Beltway Consensus: Iraq Edition,” published at Notes On Liberty: the complete post is available at http://notesonliberty.com/2013/01/27/the-beltway-consensus-iraq-edition/