Chuck Hagel, President Obama’s pick for the next secretary of defense, has begun his Senate confirmation hearings. Reports indicate the nominee believes he has some explaining to do regarding his position on the U.S. nuclear force.

Small wonder: Mr. Hagel is one of six co-authors of the radical Global Zero Commission Report, which advocates for cuts so deep to the force it would bring the U.S. far below Russian levels and could tempt China to sprint to parity or superiority.

In response to a question on Al Jazeera in 2009 about Iran’s pursuit of nukes, he said: “How can we preach to other countries that you can’t have nuclear weapons but we can and our allies can? There is no credibility, there’s no logic to that argument.” Explaining to do, indeed.

The authors of the Global Zero report argue for deploying 450 nuclear weapons, compared to the 1,550 in the recently signed New START Treaty. For those who are ideologically opposed to nuclear weapons, which Mr. Hagel by all appearances is, low numbers can only be justified if the number of targets the U.S. holds at risk is small.

Therefore, the authors of the report insist the list of plausible countries the U.S. might have a nuclear exchange with is small and constant, and the number of weapons the U.S. requires to hold at risk in those countries is also small.

But this isn’t how numbers should be determined. Senators on the Armed Services Committee should make the point that U.S. nuclear weapons are meant to deter conflict, to protect and assure allies so they don’t feel the need to acquire a nuclear capability, and to end war on terms most favorable to the United States. If the Pentagon and White House begin with this, the number could be those required by the New START Treaty or possibly higher.

Put another way, as General Brent Scowcroft and Secretary Henry Kissinger noted in a 2012 Washington Post op-ed, “the overarching goal of contemporary U.S. nuclear policy must be to ensure that nuclear weapons are never used. Strategic stability is not inherent with low numbers of weapons; indeed, excessively low numbers could lead to a situation in which surprise attacks are conceivable.”

The Global Zero Report authors also advocate the U.S. deploy its systems in such a manner that it would take 24-72 hours from the time the president determines deployment is necessary. The reason: to relieve the “intense pressure on nuclear decision-making that currently exists.”

This is meant to handicap presidents, just in case one is quick on the nuclear trigger. But contrary to the hypothetical scenario the authors are imagining, an American president would not employ nuclear weapons lightly, and in a crisis, deployment may be necessary before the self-imposed limitations.

Last, the authors promote major changes in the make-up of the force. This includes completely eliminating the ICBM leg of the traditional U.S. Triad, deep reductions in sea-based nuclear forces, and the elimination of the nuclear B-52 bomber.

For over five decades, all Democratic and Republican administrations have supported the Triad and have said that moving to two legs would be overly risky, provocative, and destabilizing. Moreover, the U.S. Senate in November 2012 passed an amendment by voice vote that affirms Senate support for maintaining and modernizing the Triad.

The contents of the Global Zero report are so extreme that it would surprise few if Mr. Hagel distanced himself from the report altogether. Perhaps he will say he only signed it as a favor to Gen. James Cartwright. Whatever the reason, he should distance himself from it, repudiate its recommendations, and then work to assure the senators that as secretary of defense he would guarantee the U.S. nuclear force is second to none, modernized, robust, and offers a credible deterrent.

A U.S. nuclear force that is not those things could inspire proliferation, cause our enemies to build up their forces to challenge the U.S., and even inadvertently spark the unthinkable: nuclear war in the 21st century.

-Rebeccah Heinrichs, an expert on nuclear deterrence and missile defense, is a Visiting Fellow at The Heritage Foundation (heritage.org).