From the Keen-Sense-of-the-Obvious Department: The wars in Iraq and Afghanistan have been hard on military marriages. The risk of divorce rises in direct relation to the length of time troops have spent deployed to combat zones, according to a new Rand Corp. study.

The results should come as no surprise, but the specifics of the study are interesting. Deployments most negatively affect women in the military. They face a greater chance of divorce than men. The study did not look at why.

Among couples married before the Sept. 11 terrorist attacks, those who experienced 12-month deployments to war zones were 28 percent more likely to become divorced within three years of marriage as compared with peers who experienced similar deployment before the wars began.

Perhaps as evidence that couples who married after the Sept. 11 attacks were better prepared for the challenges they might face, the study found that the divorce risk was lower for couples married after the terrorist attacks than for couples married before.

The length of the deployment made a difference. More cumulative months of deployment increased the risks of divorce among military couples, the study found.

Where you were deployed matters, too. The risk of divorce was higher for hostile deployments than for nonhostile ones, and women were always more likely to divorce than male service members as a result of time in deployment.

Earlier studies found that deployments had little or no effect on divorce rates or even helped to decrease the risk of divorces. But the authors of this study say this data cover a wider time frame, using information from 462,444 enlisted service members who married while serving in the military from March 1999 to June 2008.

Ninety-seven percent of the divorces occurred after a return from deployment.

There is some good news: The risk of divorce was lower among military families who had children.

Mark Brunswick • 612-673-4434