IRAQ’S PROGNOSIS is better today than it has been for a long time. An end to major violence, and with it a major reduction in the risk of a wider war and the human cost of further bloodshed, is now a real possibility. But to realize this potential won’t be cheap or easy. And it won’t produce Eden on the Euphrates. A stable Iraq would probably look more like Bosnia or Kosovo than Japan or Germany.

This is because the likeliest route to stability in Iraq is not by winning hearts and minds or reaching a grand political bargain in Baghdad. It is by building on a rapidly expanding system of “bottom up” local cease-fires, in which individual combatant factions who retain their arms nevertheless agree to stop using them and stand down. Of course, fighters who voluntarily stop shooting can voluntarily start again; such deals are not inherently stable or self-policing. But neither are these merely accidents or brief tactical breathing spells. Cease-fires in Iraq have spread so rapidly because they reflect an underlying, systematic shift in the war’s strategic calculus since early 2006 that has now made peace look better than war for the major combatants. This same strategic reality gives most of the remaining holdouts a similar incentive to stand down, which could bring an uneasy stability to Iraq.

If so, the challenge for the United States would not end. The mission would shift from war fighting to peacekeeping, and U.S. casualties would fall accordingly. But a continued presence by a substantial outside force would be essential for many years to keep a patchwork quilt of wary former enemies from turning on one another.