U.S. Marine Capt. Katie Petronio was a dynamo upon graduation from Bowdoin College in 2007. Standing 5 feet 3 inches, she could squat 200 pounds, and she seemed as ready for a combat role as many men were.

But just five years later, her body had figuratively started crumbling under the stress of service in Iraq and Afghanistan as a combat engineer officer. Her spine had compressed her nerves to the point of causing neuropathy. Her thigh muscles started to atrophy. She lost 17 pounds and was diagnosed with polycystic ovarian syndrome, which led to infertility. The experience prompted her to write a 2012 article for the Marine Corps Gazette. Its title: “Get Over It! We Are Not All Created Equal.”

Still, the Pentagon moved ahead to change U.S. history in December when it opened all combat roles to women. The issue then took on a sharper edge in April when a Republican-led congressional committee passed an amendment that would require all women ages 18 to 25 to register for Selective Service. The question now: Will the government, if it ever reinstitutes a draft, force women into the combat roles that are now open to them on a volunteer basis?

The issue of drafting women emerged in February when the top generals of the Army and Marine Corps told members of Congress they believed women should register with Selective Service, and U.S. Rep. Duncan Hunter, R-Calif., introduced the cheekily named “Draft America’s Daughters Act.” Hunter said he might vote against his own bill if it advanced through Congress but that the American people “deserve to have this discussion through their elected representatives.”

Hunter’s bill became an amendment to the annual defense appropriations bill, and Hunter did indeed vote against it last month. However, several other Republicans voted for it. Their support pushed the vote count over the edge, allowing it to pass 32-30. (Many conservatives were not amused by Hunter’s ploy. “This is the Republicans being the stupid party,” said Penny Nance, president of Concerned Women for America. “This is a Republican congressman who wanted to make a point but unfortunately betrayed women.”)

Rep. Martha McSally, R-Ariz., one of the handful of Republicans who voted for the amendment, pointed out that some of the American men drafted to serve in World War II, Korea, and Vietnam served in non-combat positions. She said in the event of another draft, the military would put people in positions that they are qualified to fill.

The distinction between combat and support roles is an important one for those opposed to women in combat, as it implies an admission that men and women have different physical capabilities—differences policymakers should acknowledge. Army statistics show that women are injured at twice the rate of men in combat training, and these injuries are mainly musculoskeletal in nature.

Even the strongest military women are still susceptible to these. Terri Christiansen of Tallahassee, Fla., served five years in the Army and eight years in the Reserves before taking a 13-year break to raise her children. She then returned to the Florida National Guard and served two deployments: one to Iraq and one to Afghanistan. These days, she’s a chief warrant officer 2 with the National Guard. She attends the 5:45 a.m. “boot camp” class at her local gym.

Had combat roles been an option for her in 1984, Christiansen would have advised her enthusiastic, 20-year-old self this way: “Do what you’re passionate about, but really think about consequences and if you are suited for that. … Women’s bodies are different than men’s. In some ways we’re really strong, like we can usually road march for longer than men. We’re tough. We can carry a lot. But I’m starting to already have back and shoulder problems. … Our bodies distribute weight differently.”

Marine Capt. Petronio, in her Marine Corps Gazette article, wrote that the issue is not whether women are capable of conducting combat operations, but for how long: “My main concern is a question of longevity. Can women endure the physical and physiological rigors of sustained combat operations, and are we willing to accept the attrition and medical issues that go along with integration?”

‘Can women endure the physical and physiological rigors of sustained combat operations, and are we willing to accept the attrition and medical issues that go along with integration?’ —Petronio

Elaine Donnelly, president of the Center for Military Readiness, points to Marine Corps tests of infantry trainees in which women were injured at six times the rate of men: “Not a single study has shown that training can overcome significant load-carriage and endurance gaps between men and women,” she wrote in a September 2015 memo to Navy secretary Ray Mabus. She also raises concerns about cost: Although thousands of women could be selected in a draft, likely only a select few would meet the high standards required to serve in combat, she said, and training so many individuals who ultimately could not serve would be costly. Donnelly has requested estimates about just how costly it might be.

But concerns about women in combat go beyond physical limitations and monetary costs. Some also have theological problems. Bentley Rayburn, a retired Air Force major general, served on a commission of chaplains convened to address the issue in the 1990s. He and others speak of a biblical basis for women to request exemptions from the draft as conscientious objectors, but only if their churches have taken a public stand on the issue. (He’s skeptical that a draft involving women would limit drafted women to non-combat roles: “I assume liberals wouldn’t put up with that.”)

“There has to be something that [a female draftee] could point to where her church says it is not a good, proper, biblical role or position for her to take,” he said. “We don’t see women in the biblical accounts in combat. There’s the obvious example that’s drug out every time about Deborah, but she wasn’t in a combat role and she did it because the men didn’t step up to their responsibilities.” The Council on Biblical Manhood and Womanhood similarly proclaims in a post from February that “Christian dads should never let their daughters die for them.”

One such Christian dad has grappled with the issue and is at peace with where God has called his daughter. Glenn Kosirog owns a pharmacy in Chicago. In a 2012 court case, he successfully won the right not to stock the morning-after pill. Kosirog’s 29-year-old daughter, Hannah, is a captain in the Air Force and a contracting officer at the National Reconnaissance Office.

While Hannah attended high school in a quiet suburb, Glenn grappled with whether to allow her to enroll in the Air Force Academy. But he now says he knows that the Air Force is where she belongs and that she thrives in high-pressure situations: “She’s a sharp thinker. She’s really been able to impulsively process things and make a decision beyond my pay grade.” Glenn said he also had a conversation with Hannah at one point about the possibility of her serving on the front lines. He asked, “We do not believe in women in combat, do we?”

Hannah’s answer: “No, we do not.”

Countries conscripting women

*Countries where combat roles are open to women

Benin Selective 18-month service

Bolivia Two-month service

Chad One-year military or civic service

China* Selective 2-year service

Cuba Two-year service

Eritrea* Indefinite; applies to everyone under 50

Israel* Two-year service

Mozambique Selective two-year service

North Korea* Seven-year service

Norway* 19-month service

Sudan One to two years compulsory or voluntary service