"Lioness," showing this week on PBS' "Independent Lens" series, is an up-close look at the evolving role of women in the U.S. military — not just in traditional roles as nurses and support personnel but as weapon-toting frontline troops.

The 82-minute piece, by veteran documentarians Meg McLagan and Daria Sommers, deals with five women attached to a Marine battalion in the middle of prolonged fighting in Ramadi, Iraq, in 2004.

Retired Navy Capt. Lory Manning, now of the Women's Research and Education Institute, says they were among the first U.S. women to experience combat on an essentially equal footing with men.

Federal law prohibits assigning women to direct combat, but that distinction has been blurred on the ground in the Iraq war. Among other things, U.S. troops, particularly in the combat-heavy phase of the war, were stretched thin and needed help. Also, there are Islamic cultural prohibitions against men searching Iraqi women or even talking to them.

As a solution, the Army began Operation Lioness, assigning female soldiers to accompany male troops on patrol and on checkpoint duty, although the women had not had infantry training.

Staff Sgt. Ranie Ruthig, a mechanic who never expected to fire a weapon, remembers a late-night mission in which troops forced their way into Iraqi homes to search for weapons and insurgents.

"I felt like the Gestapo," she said. "All I could think of was 'What would I feel like if somebody did this to me?' "

Spc. Shannon Morgan shot and killed an insurgent during a street fight.

"I don't regret what I did," she says, "but I wish it hadn't happened."

"Lioness" follows the five after their return to the U.S.

Home front scenes are spliced with combat footage from Ramadi.

Capt. Anastasia Breslow reads from her journal: "Our hearts are in the right place, we kill for peace, we kill for each other. Even sitting here writing this I am still amazed that I am part of this."

If there is to be a postwar dialogue about the role of women in war, "Lioness" is one starting point.

"We are waiting for the policy to catch up to the real-world practice," Manning says.