As one of his last acts as secretary of defense, Leon Panetta lifted the ban on women serving in combat roles. Considering that the hue and cry over that prospect — along with the false specter of unisex bathrooms — helped kill the Equal Rights Amendment in the 1970s, the initial public reaction was surprisingly muted.

Perhaps that is because the change has been a long time coming, due to changing social attitudes and the changing nature of modern warfare.

If there is an instant cause for the new acceptability of women in combat, it is the wars in Iraq and Afghanistan, where there were no front lines, no traditional safe havens because fighting with guerrilla insurgents could break out anywhere and once a unit moved outside the wire on patrol there were no noncombat free riders.

Once the shooting began, the Pentagon ban on women serving in combat units below the brigade level — about 3,500 troops — began to erode.

The insurgents made no distinction between regular riflemen and intelligence officers, medics, military police and the female soldiers along to interrogate Iraqi and Afghan women. The Pentagon distinction between combat and noncombat became more and more blurred and broke down quite quickly under the exigencies of this new kind of warfare.

If there is a poster woman for this change it is Tammy Duckworth, a former Army helicopter pilot and now a member of Congress, who lost both legs flying combat missions in Iraq in 2004. More than 280,000 women have served in combat zones since 9/11, and 152 have died in the course of that service.

The immediate effect of the order is to open up 230,000 positions women are now excluded from, most of them in the combat arms where service has been considered a prerequisite for promotion to the senior ranks.

The Pentagon is studying whether women should be excluded from elite and demanding units like the SEALs, Delta Force and other special ops units. Anecdotally, the feeling among top-flight frontline units is that the women will be accepted if they can do handle the physical aspects of the training without special accommodations of any kind. Indeed, that should be a key consideration for all front-line service, not just for special ops.

Even so, we’re talking about a relatively small fraction of the services. About 14 percent of the military is female. But the opportunity to train under dirty, onerous and exhausting conditions to place oneself in danger to defend one’s country should be open to all who can qualify.