Secretary of Defense Leon Panetta announced the end of a ban on women in combat roles. (The Washington Post)

Outgoing Defense Secretary Leon E. Panetta announced Thursday a lifting of the ban on female service members in combat roles, a watershed policy change that was informed by women’s valor in Iraq and Afghanistan and that removes the remaining barrier to a fully inclusive military, defense officials said.

Panetta made the decision “upon the recommendation of the Joint Chiefs of Staff,” a senior defense official said Wednesday, an assertion that stunned female veteran activists who said they assumed that the brass was still uneasy about opening the most physically arduous positions to women. The Army and the Marines, which make up the bulk of the military’s ground combat force, will present plans to open most jobs to women by May 15.

The Army, by far the largest fighting force, currently excludes women from nearly 25 percent of active-duty roles. A senior defense official said the Pentagon expects to open “many positions” to women this year; senior commanders will have until January 2016 to ask for exceptions.

“The onus is going to be on them to justify why a woman can’t serve in a particular role,” said the official, who spoke on the condition of anonymity to discuss the plan before the official announcement.

The decision comes after a decade of counterinsurgency missions in Iraq and Afghanistan, where women demonstrated hero­ism on battlefields with no front lines. It dovetails with another seismic policy change in the military that has been implemented relatively smoothly: the repeal of the ban on openly gay service members.

Lawmakers and female veterans applauded Wednesday’s news, saying the ban on women in combat roles is obsolete.

“This is monumental,” said Anu Bhagwati, a former Marine captain and executive director of the Service Women’s Action Network, which has advocated for the full inclusion of women. “Every time equality is recognized and meritocracy is enforced, it helps everyone, and it will help professionalize the force.”

Critics of opening combat positions to women have argued for years that integration during deployments could create a distracting, sexually charged atmosphere in the force and that women are unable to perform some of the more physically demanding jobs.

Advocates and experts say women are unlikely to flock to those positions, such as roles in light infantry and tank units and Special Forces — although some may. More substantively, they say, lifting the ban will go a long way toward changing the culture of a male-dominated institution in which women have long complained about discrimination and a high incidence of sexual assault.

Changes long sought

Lawmakers and advocates have long pressed the Pentagon to create a more inclusive force, yielding incremental changes. The American Civil Liberties Union recently sued the Pentagon over its policy, calling it discriminatory.

Last year, military officials opened numerous job categories to women after a study concluded that the Defense Department was ready for greater inclusion in combat units. That made it easier for women to be assigned, for example, to combat brigades as radio operators. It also gave commanders a sense of how a broader integration process could work, said an Army general who played a key role in last year’s effort to open new positions for women.

“The average professional will say, ‘I’ve served with women at all levels, and based on my experience, women have done a phenomenal job,’ ” said the officer, who spoke on the condition of anonymity because the change had not been formally announced.

The debate over the supposed pitfalls of women and men sharing close quarters has been rendered moot by the recent wars, he said, adding: “If you were having this debate in peacetime, it might be more emotional.”

The fact that women have excelled in de facto front-line roles in Iraq and Afghanistan has proved such concerns unwarranted, Sen. Carl Levin (D-Mich.), the head of the Senate Armed Services Committee, said in an interview Wednesday afternoon.

“The reality is that so many women have been, in effect, in combat or quasi-combat,” he said. “This is catching up with reality.”

In a statement, Sen. James M. Inhofe (Okla.), the leading Republican on the Armed Services Committee, voiced a measure of concern, saying last year’s study raised “serious practical barriers” that, if ignored, could jeopardize the “safety and privacy” of service members.

Sen. John McCain (R-Ariz.), another member of the panel, said he supports the decision, but he alluded to some of the thorny implementation issues that have yet to be addressed.

“It is critical that we maintain the same high standards that have made the American military the most feared and admired fighting force in the world — particularly the rigorous physical standards for our elite special forces units,” he said in a statement.

The senior defense official said the Pentagon expects to have gender-neutral standards for combat jobs.

‘The time has come’

Overall, women make up about 14 percent of the active-duty military. According to the Defense Department, 152 female troops have been killed in the Iraq and Afghan wars.

The Pentagon announced last February that it would open about 14,000 combat-related positions to female troops. But an estimated 238,000 other jobs — about one-fifth of the regular active-duty military — were kept off limits to women. Virtually all of those jobs were in the Army and Marine Corps.

Panetta, who is expected to step down soon, has long favored a more inclusive military, and after last year’s review, the senior defense official said, the Joint Chiefs and service chiefs began seeing eye to eye on the issue.

In a Jan. 9 letter to Panetta, Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, wrote that the chiefs “unanimously” supported his goal of integrating women into “occupational fields to the maximum extent possible.”

“The time has come to rescind the direct combat exclusion rule for women and to eliminate all unnecessary gender-based barriers to service,” he wrote.

“It is a paradigm shift for the military,” the senior defense official said, “one that everyone is ready to make.”

Julie Tate contributed to this report.