From France's Joan of Arc to female resistance fighters in World War II and the black-clad women warriors of the Viet Cong, history is filled with stories of women fighting alongside men.
In many modern armies, however, ground infantry combat is still largely a male preserve - either by regulation, practical issues such as physical requirements of living space or personal preference in volunteer forces.
But change is afoot. Wars in Iraq and Afghanistan, where supply troops, clerks and military police have ended up in battle regardless of gender, have blurred the distinction between combat and non-combat jobs.
This week the Pentagon lifted the ban on women being assigned to smaller ground combat units, although U.S. service chiefs have until January 2016 to recommend whether some positions should remain closed to women, such as Navy commandos or the Army's Delta Force.
Here are examples of how some other countries have set rules for women in war:
The image of the gun-toting Israeli woman warrior is widely seen as the prototype of a gender-blind military. Reality is different. Israeli women are subject to the draft - but they serve two years while men serve three. Women were also barred from direct combat until 2000, when the first and so far only mixed gender infantry battalion was organized. The Caracal battalion, which is about 60 percent female, was assigned to patrol the relatively quiet borders with Jordan and Egypt. Still, more than 90 percent of Israel's military jobs are open to women - including high-risk posts such as air force pilots, air defense, naval gunboat crews, artillery and search and rescue. But the five major infantry brigades are still all-male.
Canada considers itself a pioneer in opening military ranks to women, allowing female soldiers to serve in combat jobs in 1989. Nearly a generation later, women hold about 14 percent of all active duty positions in the Canadian military but only 2.4 percent of the combat slots. At least three Canadian women soldiers have been killed in Afghanistan, two by roadside bombs and one in a firefight.
Women make up about 9 percent of Britain's all-volunteer military but are barred from ground force units whose primary mission is to "kill the enemy." Nevertheless, they can serve on warships, artillery, as engineers and on combat aircraft. A review by the defense ministry in 2010 found "no evidence" that allowing women to serve in ground combat units such as the infantry or Royal Marines "would be beneficial or risk-free." Still, women have served in medical and support jobs with the British military in dangerous areas of Iraq and Afghanistan, where they face rocket barrages, roadside bombs and ambushes.
Women make up about 15 percent of all troops in France's military, the highest proportion of any European country. Women are not legally barred from serving in combat infantry units and the submarine service. However, Defense Ministry spokesman Gen. Martin Klotz said many women can't carry the 110 pounds (50 kilograms) of basic equipment, and submarines lack space for women's sleeping quarters. The medical corps accounts for the highest female representation among the services - about 53 percent - with the air force second at 21 percent.
Germany's postwar army excluded women until the mid-1970s, when a few were allowed to join the medical corps and military bands. The restriction was not lifted until 2000, when a female electrician challenged the ban at the European Court of Justice. The following year the Germans lifted all restrictions on women in the ranks if they could meet the same physical requirements as men. More than a decade later, women make up about 9 percent of the armed forces. A military spokesman was unable to say how many are in ground combat units.
New Zealand lifted all restrictions on women serving in the military - including infantry units - in January 2000. But spokeswoman Kirsty Taylor-Doig said no woman has ever passed the rigorous selection criteria to join the elite special operations service, which performed with distinction in Afghanistan. Women make up nearly 16 percent of the combined force, with the largest group in the navy, which is about 22 percent female. Last August, a woman medic was killed by a roadside bomb in Afghanistan, the first New Zealand female service member to die by hostile fire since World War I.
NORDIC AND BALTIC COUNTRIES
The nations of northern Europe have spearheaded gender equality in the military, with Norway lifting all restrictions in 1985, including for special operations jobs. Denmark, Sweden and Finland followed suit. The former Soviet states of Lithuania and Estonia lifted restrictions and sent women to combat roles in Iraq and Afghanistan, though many women in Estonia have complained they are encouraged to apply for desk jobs.
Associated Press correspondents Ian Deitch in Jerusalem, Matti Huuhtanen in Helsinki, Finland, Jamey Keaten in Paris, Nick Perry in Wellington, New Zealand, and David Rising in Berlin contributed to this report.