Women struggled to formally serve their country in the American Revolutionary War. They were forbidden to serve, but did so against the law. The existence of women was even suppressed by General Washington himself.
However, as women followed the Army for shelter and other basic necessities they were equally important to the army.
During the Civil War women once again served. Like the American Revolutionary War they served in support roles and served in combat even though both the Union and the Confederate armies prohibited it. Women in combat had to dress like men and change their names.
The Spanish-American War women still continued to disguise themselves as men to fight for their country.
Why June 12th?
The Women’s Armed Services Integration Act, June 12, 1948:
Congress gave members of the Women’s Army Corps (WAC), a branch of the U.S. Army, full service status during World War II. However, the legislation that did so was set to expire in 1948. As early as 1946, Army leaders requested that enlisted women be made a permanent part of the Army. Following two years of legislative debate, Congress passed the Women’s Armed Services Integration Act in 1948. The act granted women the right to serve as permanent, regular members of the Army, Navy, Marine Corps, and the recently formed Air Force.