War movies are a genre in which women will rarely if ever play major roles.
However there are a few that come to mind immediately.
The nurse is by far the most common role. In many movies they are very prominent. Especially in the sub genre of the war romance they get more than just small roles. (Yes, Pearl Harbor (2001) comes to mind, but…)
Mothers, wives, fiancées are often found at the very beginning of a movie, when the soldiers leave their homes like in Dark Blue World aka Tmavomodry svet (2001). We often see them again, reading a letter arriving from the field as in The Thin Red Line (1998). They serve as a sort of counterpoint to make the contrast between those who fight and those who stayed home even bigger. Then, you may find them once more at the very end, when the soldiers return home. One of the most poignant and touching wives is Madeleine Stowe in We Were Soldiers (2002). The story moves back and forth between the battle field and the home front depicting the agony the soldier´s wives went through when the telegrams arrived telling them one of their husbands had been killed.
Nurses become very often soldiers’ girl-friends which makes the two roles blend into each other. But many of the classic girl friends in movies depicting the second WW are the girls the men encounter in the countries they are shipped to. The American soldiers in The Pacific for example have Australian girl friends.
The role of the resistance fighter is quite a noble one. Not very frequent but appealing. Cate Blanchett as Charlotte Gray (2001) comes to mind. Or the women in Uprising (2001). And definitely Sophie Scholl (2005). The latest example of this kind is Carice van Houten as the jewish woman Rachel Stein who joins the Dutch resistance after having survived a massacre in the brilliant Black Book aka Zwartboek (2006).
Female soldiers that are even involved in combat are not very frequent. The most remarkable one I remember is the Vietnamese sniper in Full Metal Jacket (1987). A further female soldier is played by Demi Moore in G.I. Jane (1997) where she is said to be the first woman to have been granted access to the navy SEALS.
Women as officers is by far more common. Again Demi Moore played a role in the excellent legal drama A Few Good Men (1992). And then there is Meg Ryan as medevac chopper pilot Capt. Karen Walden in Courage under Fire (1996).
Unfortunately some of the above mentioned portraits of women in war movies are quite questionable and have been criticised repeatedly (especially G.I. Jane).
I almost forgot the victims. Inexcusable. There are as innumerable female victims in real wars as there are high numbers in movies. One of the saddest are the victims in Vietnam war movies. I think of Platoon (1986) and Casualties of War (1989). They are not the only ones. Of course not.
My favourite heroines are Cate Blanchett as Charlotte Gray, the wonderful Juliette Binoche as nurse in The English Patient and, another nurse, Sandra Bullock in In Love and War, and the outstanding Julia Jentsch as Sophie Scholl. The first two are based on novels, the other two on historical facts. Sandra Bullock plays the nurse Ernest Hemingway fell in love with when he fought in Italy during WWI.