Female military personnel. (AP Photo/Stephen B. Morton)

If your daughter, granddaughter, or the girl-next-door has to register for a possible future draft, you can blame Arizona Senator John McCain, Chairman of the Senate Armed Services Committee.

During a closed-door committee session on May 19, Chairman McCain sponsored, without prior notice, legislation to impose Selective Service obligations on young women, ages 18-26. Six Republicans and all Democrats supported McCain’s gratuitous addition to the 2017 Defense Authorization bill (SR 2814), citing the Defense Department’s recent unilateral decision to gender-integrate direct ground combat units such as the infantry.

Seven Republicans, led by Mike Lee of Utah, voted to strike the measure in committee, but elements of surprise and confusion apparently helped McCain’s power-play. (Sen. Lee and several colleagues reportedly will try again when the full bill comes up on the floor.)

Why the rush to set up women for conscription? A written statement obtained by The Hill said that Chairman McCain was acting on a “recommendation” from the Marine Commandant and the Army Chief of Staff regarding Selective Service. That was an overstatement.

Marine General Robert Neller and Army General Mark Milley, who testified before the committee on February 2, responded to a question about Selective Service obligations for women by expressing personal opinions, not recommendations. Civilian leaders of their services seated at the same table demurred, but Chairman McCain nevertheless invoked the generals’ “recommendation” as justification for his controversial legislative move.

Last fall the Marines did make official recommendations on the underlying paramount issue – whether military women should be involuntarily assigned to direct ground combat (infantry) units that attack the enemy with deliberate offensive action. Backed by research and definitive empirical data, the Marines exercised their option to request exceptions to the administration’s women-in-combat mandates.

During nine-months of scientific field tests with male and female Marines, all-male task forces outperformed mixed-gender units 69 percent of the time. Injury rates among women were two to six times greater -- even higher in load-bearing task force combat units such as the infantry.

The Marines concluded that significant differences in physical strength, speed, endurance, deployability and marksmanship when fatigued would seriously impede ground combat “survivability and lethality.” President Obama, however, brushed aside research findings.

Defense Secretary Ashton Carter ignored the Marines’ best professional advice, and a strongly-worded memorandum setting forth their concerns was not posted on the Defense Department webpage listing other research findings.

The Senate Armed Services Committee should have conducted hearings with independent experts to openly discuss reasons why the Marines requested exceptions. Instead, they voted behind closed doors to register civilian women for possible conscription, disregarding the impact on readiness.

Imagine a catastrophic national emergency that exceeds the capabilities of our severely-depleted All-Volunteer Force. Selective Service registration is a relatively low-cost insurance policy. Its purpose is not to indulge gender war resentments or to fill support positions. The sole legitimate purpose of conscription is to rapidly find and train replacements for combat troops who are dying in battle.

The Supreme Court, in its landmark Rostker v. Goldberg decision (1981), upheld the constitutionality of women’s exemption from Selective Service registration. The Court noted that since women were not “similarly situated” in land combat units, exemption from the draft did not violate equal protection principles.

Under the McCain mandate, a national emergency requiring reactivation of Selective Service would have to call up young men and women in equal numbers. This would waste scarce time and resources trying to evaluate and train thousands of women just to find the small percentage who might be minimally qualified for the combat arms where the critical need is greatest.

None of this is necessary, since women always have volunteered to support war efforts, and will do so again.

The Supreme Court did not consider other reasons to exempt women, but it did affirm the constitutional right of Congress to decide. Even under new rules affecting women, Congress should promote military readiness by establishing a fact-based record that sustains women’s exemptions from direct ground combat and Selective Service.

The issue here is not “men’s rights” or “women’s rights.” It is national security and being prepared to defeat unforeseen existential threats, perhaps from multiple directions. Instead of voting to draft America’s daughters, members of the House and Senate should affirm sound policies that put military readiness first.

Elaine Donnelly is President of the Center for Military Readiness, an independent public policy organization that reports on and analyzes military/social issues.