Evolution of U.S. military

1973: U.S. ends military draft.

1975: President Ford signs law permitting women to enroll in U.S. military academies beginning in fall 1976.

1978: Marine Corps Col. Margaret Brewer becomes a brigadier general, the first female general in the Corps' history.

1980: First coed classes graduate from U.S. service academies.

1981: Department of Defense issues directive stating that "homosexuality is incompatible with military service" and that service members will face mandatory discharge.

1988: Department of Defense report says homosexuals pose no significant security risk. Military leaders challenge research.

1993: President Clinton signs "Don’t Ask, Don’t Tell" into law.

1994: Defense Secretary Les Aspin announces less-restrictive combat policy, allowing 80 percent of all military positions to be filled by men or women.

1996: Marine Corps Lt. Gen. Carol Mutter becomes the first female three-star general.

2006: Angela Salinas works her way through the ranks and becomes Marine Corps’ first female Hispanic brigadier general.

2008: Army Gen. Ann Dunwoody becomes the first female four-star general.

2010: President Obama signs repeal of “Don’t Ask, Don’t Tell,” into law, allowing gay and bisexual members to serve openly.

2010: Navy Secretary Ray Mabus announces that for the first time, women can be assigned to submarines.

2013: Defense Secretary Leon Panetta allows women to serve in direct combat roles.

2014: Michelle Howard becomes the Navy's first female four-star admiral.

2015: The Army opens 40 slots for female candidates in the Army Ranger Training Assessment Course, which precedes Ranger School.

July 13, 2015: Defense Secretary Ash Carter announces a plan to study allowing transgender troops to serve openly.

Aug. 21, 2015: Capt. Kristen Griest and Lt. Shaye Haver are the first women to graduate from the Army’s Ranger school.

Dec. 3, 2015: Carter announces all combat jobs will be open to women in 2016.