The change is intended to help women advance their careers, which has been made more difficult by their lack of combat experience. The report found that retention rates of women in the military after 20 years of service is significantly lower than that of their male counterparts. The Army didn't promote its first four-star female general, Gen. Ann Dunwoody, until 2008; she rose through the ranks as a logistician.

The role of women in the U.S. military evolved dramatically over the past decade. As the demand for troops grew, particularly during the war in Iraq, women undeniably served on the front lines. Their commanders maneuvered around the Pentagon rules by attaching units with women in them to combat battalions, where women could do the work but wouldn't receive combat decorations or other credit for being in combat.

The U.S. military lags behind many of its coalition partners in Afghanistan on this issue. Canada, Denmark, Germany, France, Italy and Australia all allow women to serve in combat roles.

The changes have the least impact on the Navy and Air Force, where most jobs are open to women. The Air Force is now planning to promote its first female four-star general, Lt. Gen. Janet Wolfenbarger. Wolfenbarger also is a logistician.

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