There are no women in these ground combat jobs.Women, of course, have been flying combat missions in fighter jets, attack helicopters, for more than 20 years, but beginning this week, those ground combat jobs in infantry, artillery and armor will be open to women. Officials don't expect a rush of women interested.

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The Marines estimate that roughly a hundred or 200 women will be interested in going into these jobs - roughly 2 percent of those jobs. Still, this is historic. It's a biggest cultural change in the military maybe ever, probably bigger than integrating the force back in 1948 when African-Americans were no longer segregated in separate units.

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Marine and Army women have deployed with infantry units in Iraq and Afghanistan in what's called female engagement teams, going into villages, talking with women and sometimes coming under fire.

The Marines already have started putting women through infantry training. They've done it for the past couple of years. And it's tough. Roughly one-third of women have made it through that infantry training. So you're not going to see a lot of women actually make it through this.

Women and men will have to go through the same physical test before they get into these ground combat jobs, and the test will increase over time for again both Marine Corps and the Army just to make sure everyone is physically fit enough to go through these jobs, to get through this training.