War By the Numbers

Patricia Sullivan, assistant professor at the University of Georgia, has completed a major study of all 122 wars and military conflicts since World War II in which a major power was in conflict with a weaker power. She found the weaker power prevails 39 percent of the time.

“If you know some key variables—like the major objective, the nature of the target, whether there’s going to be another strong state that will intervene on the side of the target and whether you’ll have an ally—you can get a sense of your probability of victory,” said Sullivan, whose study appears in the Journal of Conflict Resolution.

Sullivan said the most important factor influencing whether the more powerful nation will be successful is whether its strategic objective can be accomplished with brute force alone or requires the cooperation of the adversary.

What does her research say about the current conflict in Iraq?

Sullivan said several factors contribute to the relatively low probability of success in the current Iraq war. Most importantly, the objective requires the support of the population and can’t be accomplished by force alone. Factional infighting, the insurgency and possible insurgent support by countries such as Iran and Syria further undermine the chance of success.

“No one could have predicted exactly what would happen after we overthrew the regime of Saddam Hussein,” Sullivan said. “But what my model could say was that if the population was not supportive of whatever new regime we put in power and the American strategic objective shifted from regime removal to maintaining the authority of a new government, the likelihood of a successful outcome would drop from almost 70 percent to just under 26 percent.”

So, if relying on brute force lowers your likelihood of success, does that mean the "surge" wasn't such a great idea after all? Hmmm.