WASHINGTON — Reflecting the steady but glacial evolution of the role of American women in war, the Pentagon took a small step Thursday and announced that women would be formally permitted in crucial and dangerous jobs closer to the front lines. But it stopped short of officially allowing women to serve in combat.

The decision, the result of a yearlong Pentagon review ordered by Congress, allows women to be permanently assigned to a battalion — a ground unit of some 800 personnel — as radio operators, medics, tank mechanics and other critical jobs.

In actual practice, however, women already serve in many of those jobs, but as temporary “attachments” to battalions — a bureaucratic sidestep that has been necessary with the high demand for troops during the last decade of war in Iraq and Afghanistan. The Pentagon’s new rules largely formalize existing arrangements and in many ways are simply catching up with realities on the battlefield.

The new rules keep in place a ban on women serving in the infantry, in combat tank units and in Special Operations commando units. Nonetheless, many women in Iraq and Afghanistan have served in combat as attachments to infantry foot patrols, and in many cases they have come under fire and fought back. More than 140 women in the American military have lost their lives in Iraq and Afghanistan.