18th Century: During the Renaissance and throughout most of Western history since then, women have not been allowed to fight in armies. In fact, women are legally barred from enlisting in the military for most of American history. Europeans, as well, made military service by women illegal.

19th Century: Florence Nightingale founds the nursing corps of the British Army during the Crimean War. Clara Barton assembles a similar unit in the United States during the American Civil War.

20th Century: Women have made significant strides towards increasing their numbers and presence in all branches of the military. Women not only serve in the general corps of the army, navy, and marines, many can be found in highranking supervisory positions. In the last half of the twentieth century, a handful of women braved established military and societal codes to integrate branches and schools that had...