The most prominent civil wars in recent years have not started with a clear, firing-on-Fort-Sumter beginning. Instead they have been slid into as protests grow, confrontations between the regime and an opposition become more physical, and the government’s use of lethal force is increasingly matched by oppositionists firing back. This was the pattern in the civil war in Iraq unleashed by the U.S. invasion and later in Libya and Syria.

Now the same process may be occurring again in Iraq. A spurt of lethal violence this week between the Shia-dominated regime and a Sunni resistance has featured such war-like encounters as helicopter-borne government troops firing on a Shia village. This is another stage in an escalating confrontation between the opposing sectarian forces in Iraq.

Again, there is no one point in the escalation at which anyone can declare that a civil war has now begun. But that does not mean one is not beginning.

Former U.S. President George W. Bush (C) waves between his father, former U.S. President George H.W. Bush, and former first lady Laura Bush at the dedication of the George W. Bush Presidential Center on the campus of Southern Methodist University in Dallas, Texas April 25, 2013. REUTERS/Mike Stone

Any new civil war in Iraq at this time would not really be altogether new but instead a resumption of the unresolved conflict that earlier reached a peak about six years ago. Resumption would be a reminder both of the overall results of the U.S. invasion and of the later surge of U.S. troops. We have known all along that the surge never led to the political reconciliation within Iraq that it was supposed to facilitate. Now we can say also that whatever improvement in security it fostered was temporary.

There are still two grounds for optimism that Iraq will not fall over the brink into a round of fighting anything like the earlier round. One is that unlike during Iraq’s earlier political history that the U.S. invasion and subsequent fighting disrupted, and also unlike present-day Syria, the majority religious sect in the country is also the dominant sect in the regime. This is not a situation of a subjugated majority trying to get its day of dominance. A minority that sees itself as repressed can still cause quite a ruckus, but maybe there is less potential for full-blown civil war than when there is a clear disjunction between demographic patterns and patterns of political power.

The other possible reason for optimism concerns the extensive ethnic and sectarian cleansing that occurred in the earlier round of fighting. With the confessional communities now being more thoroughly sorted out and separated than before, there is less of the street-by-street hostile interface that feeds civil war at the retail level.

Even if Iraq does not go over the brink, its teetering on the brink needs to be included in any comprehensive balance sheet on the Iraq War. Rather like the heavy cost of caring for wounded American veterans, the sectarian violence and instability in Iraq is an open-ended cost that keeps adding up as the years go by.

The purpose of noting this should not be just to refight old policy wars over the Iraq War. It should be to try to learn a lesson applicable to other situations. Syria is the most obvious relevant current situation, but there are sure to be others in the future.

The basic lesson, briefly stated, is that where there is strong communal antagonism but a weak political culture for managing such antagonism, even a big effort by outsiders is unlikely to have a lasting beneficial effect on political stability.  

— Paul R. Pillar, in his 28 years at the Central Intelligence Agency, rose to be one of the agency’s top analysts. He is now a visiting professor at Georgetown University for security studies. (This article first appeared as a blog post at The National Interest’s Web site. Reprinted with author’s permission.)