The insurgents' choice of adversary is unusual. But the recent surge in violence at least follows a time-tested pattern. The insurgents are apparently trying to swamp any progress toward stability with evidence and images of chaos. The killing in that time of at least 250 policemen, soldiers and recruits also fits a pattern, since insurgents have customarily made targets of accused collaborators to isolate a regime. Less obvious is the goal in the killing of some 150 civilians.

The relationship between insurgents and the general population is always complex. Mao Zedong famously postulated that guerrillas move among the people as fish move through water. But he also warned that "a revolution is not a dinner party," and many insurgents, including the Vietcong, effectively used terror — often selectively applied — against civilians to compel segments of the population into at least passive support.

From his experience fomenting Arab revolt against the Turks, T.E. Lawrence concluded that insurgents needed only 2 percent active support from the population, and 98 percent passive support.

Sunnis vs. others

What is curious about the Iraqi tactic is that it appears aimed at creating active opposition. The insurgency is powered by Sunnis; the civilians they have killed have been overwhelmingly Shiites and Kurds. The goal appears to be to split apart the fragile governing coalition and foment sectarian strife.

Yet if the insurgents achieve all-out civil conflict, the likely losers are the Sunnis themselves, since they are a minority. Having governed for decades in Iraq, Sunnis are accustomed to the whip hand and may simply assume they will be able to regain control. Or perhaps they are betting that chaos will lead to partition, allowing Sunnis to govern themselves.

David Galula, author of a systematic 1964 study, "Counterinsurgency Warfare: Theory and Practice," noted the effectiveness of force and intimidation as tools of an insurgency. But he added a crucial caveat: "There is, of course, a practical if not ethical limit to the use of force; the basic rule is never to antagonize at any one time more people than can be handled."

That was one of several mistakes that the communist rebels made in Greece in the late 1940s. Once the country was liberated from the Germans, the communists had no majority cause, and they chose to confront a democratically elected government. Lacking much industry, Greece had few proletarians, and the peasants were not particularly restive.