Yesterday the Senate Judiciary Committee sent Elena Kagan’s Supreme Court nomination to the floor of the Senate for a vote. Republican Senators should use every measure possible to defeat her confirmation.

There are several reasons why she does not belong on the Supreme Court. But for this Iraq war veteran, the crucial one is that Ms. Kagan used her position of authority as dean of Harvard Law School to impede, rather than empower, the warriors who fight, and have fallen, for our freedoms. These actions make her an unacceptable replacement for the court’s only remaining military veteran, Justice John Paul Stevens.

Three weeks ago, I testified before the Senate Judiciary Committee about her antimilitary actions. Ms. Kagan and her supporters have whitewashed her drastic attempts to block recruiters from Harvard. Allow me to dispel the misinformation.

At her hearing on June 29, Ms. Kagan testified that “The military had full access to our students at all times.” To the contrary, Ms. Kagan persistently blocked its access to the law school’s Office of Career Services and the wide array of services it provides. Almost all students use this office to identify employers, so it’s hard to imagine how Ms. Kagan believes the military had “full access.”

Moreover, she encouraged students in speeches to protest, and obstruct, the presence of military recruiters. The Army called her actions “stonewalling;” I call them downright discriminatory.

Her backers say Ms. Kagan supports the military because she has praised them publicly and hosted dinners for veterans. A handful of veterans have defended her, and I concede that she has had good things to say about our troops, which I appreciate. But actions always speak louder than words. Ms. Kagan’s actions toward recruiters while wars were raging trump her rhetorical support.

Gen. David Petraeus calls counterinsurgency “a thinking man’s war,” and defeating our enemies on the battlefield and in the courtroom takes America’s best minds. Ms. Kagan’s action to block military recruiters happened to coincide with my deployment to Guantanamo Bay, itself a legal maze of graduate-level proportions. Would not the legal situation there be better off with more participation from lawyers of Harvard caliber?

Ms. Kagan has repeatedly stated that, despite her decision to bar recruiters from the Office of Career Services, the number of military recruits actually increased during her tenure. But this happened in spite of Ms. Kagan, not because of her. The number would have been even higher had she supported recruiters, rather than actively opposing them. The numbers are useless, except as a testament to the students who proactively sought out a military career in her hostile environment.

Ms. Kagan’s opposition to military recruiters was based on her opposition to “Don’t Ask, Don’t Tell.” I do not begrudge Ms. Kagan’s opposition to the federal law that prohibits homosexual conduct or activity in the armed forces, and that also requires separation from the armed forces for individuals who engage in this conduct or activity. Reasonable people disagree with it. However, in emails to students and statements to the press, Ms. Kagan fiercely slammed “the military’s discriminatory recruitment policy.” As a legal scholar, she knows better.

She knows that the policy she “abhors” is not the military’s policy, but a policy enacted by Congress and imposed on the military. In fact, after the law was passed in 1993 Ms. Kagan went to work for the very man who signed it into law—President Bill Clinton. Her calling it “the military’s policy” is intellectually dishonest, and she knows it.

Likewise, while Ms. Kagan sought to block full access to military recruiters, she welcomed to campus numerous lawmakers who voted for the law she calls “a moral injustice of the first order.” Additionally, Harvard Law School has three academic chairs endowed by money from Saudi Arabia—a country where being a homosexual is a capital offense. So, rather than confront the congressional source of the policy—or take a stand against a country that executes homosexuals—Ms. Kagan zeroed in on military recruiters for a policy they neither authored nor emphasized.

We are a nation at war with a vicious enemy, on multiple fronts. I’ve seen this enemy first hand, as have a precious few from my generation. The real “moral injustice” would be granting a lifetime appointment to someone who, when it mattered most, treated military recruiters, and by extension all veterans, like second-class citizens.

Mr. Hegseth, a captain in the Army National Guard and executive director of Vets for Freedom, served in Iraq with the 101st Airborne Division from 2005-2006. He is currently a graduate student in public policy at Harvard University’s Kennedy School of Government.