When the Hart-Rudman Commission predicted in 1999 that "Americans will likely die on American soil, possibly in large numbers," its members were not thinking of 9/11. They reflected a growing concern that state and non-state enemies, faced with America's preponderance of power, might seek out chemical, biological, or nuclear arms that could kill hundreds of thousands of Americans.

They recognized that, with the exception of a ballistic missile tipped with a nuclear weapon, virtually none of the so-called weapons of mass destruction (WMD) might be out of reach for a well-organized and even moderately well-funded non-state group. Some could even be fabricated by enemies with modest means and only a modicum of skill. As for state-sponsored programs, even some of the world's poorest countries, like North Korea, were capable of undertaking very sophisticated nuclear and ballistic missile programs.

Their assessment was not a one-off. Others have issued similar warnings, including the recent Graham-Talent Commission. Their 2008 study, A World at Risk, argues that this is no time to be complacent about WMD. In the decades ahead, efforts to deal with these threats have to be a cornerstone of providing for the common defense.

It Can Happen Here

The arguments against preparing for these dangers offer cold comfort. Arguing, for example, that WMD attacks may be "high consequence" but "low probability" makes little sense. There is no way to establish probability because there is no predictable data set to measure. The style of terrorist attack often turns on the choice of tactic and the terrorists who choose WMD; probability can go from zero to certainty overnight. Playing the odds on such threats is the worst kind of Russian roulette, particularly when looking at the cost of losing. By one estimate, the cost of recovering from a nuclear attack on New York City could equal the U.S. GDP.

Nor does it make much sense to argue that terrorists will adopt "simpler" means or that enemy states can be easily deterred by the U.S. nuclear arsenal. Terrorists have already gone the WMD route. The Rajneeshee cult in Wyoming in 1984 launched a biological warfare attack. In 1995, the Aum Shinrikyo hit the Tokyo subway with poison gas. Soon after the 9/11 attacks, letters laced with anthrax began appearing in the U.S. mail. Luckily, these efforts were neither very sophisticated nor well organized. Next time, we might not be so lucky. Likewise, the U.S. nuclear deterrent has not dissuaded North Korea or Iran from pursuing very aggressive nuclear and ballistic missile programs.

Perhaps the worst of these arguments is the "just-in-time" argument: When a clear and present danger presents itself, it can be dealt with then. Even the best strategic intelligence is not perfect. The U.S., for example, has failed to predict when virtually every nuclear power would conduct its first weapons test. Similarly, some dangers, such as the recent swine flu pandemic, might appear with no warning at all.

Moreover, waiting for the threat to appear before adopting countermeasures may actually speed the advance of danger. If enemies perceive that the U.S. has no defense or at best very limited capabilities, they may actually accelerate their programs so that they can quickly achieve a real capability to hold America at risk.

Possibly the best example of this worst of all ideas is the Administration's decision to slash the missile defense budget by 15 percent (about $1.4 billion), arguing that current defenses are sufficient to meet the near-term North Korea and Iran nuclear threats. This assessment may be wrong. In addition, both countries may view the U.S. program's loss of momentum as a vulnerability that they can exploit if they speed up research and deployment of their own ballistic missiles. This represents a great deal of risk for little or no benefit.

The Right Strategy

Alternatives to providing for the common defense don't offer much promise either. In particular, relying on arms control, arms reduction, and other non-proliferation activities alone offers virtually no promise of lessening global dangers. Since the end of the Cold War, the United States has dramatically reduced its nuclear inventory. That has not stopped the march to join the nuclear club. Three countries have joined since 1989, and Iran is knocking at the door.

Likewise, the non-proliferation treaty has not stopped countries from getting weapons. Both Iran and North Korea were signatories to the treaty. Today, both have active weapons programs.

The right strategy for dealing with WMD starts with stopping the terrorists. They may elect to use car bombs or dirty bombs. We should not wait for them to make their choice. The way to stop terrorists that threaten the U.S., its interests, or its allies is by taking out their leadership, disrupting their operations, breaking up their organizations, cutting off their sources of recruiting and funding, and discrediting their ideas.

Next, the U.S. must lead the effort to destroy the marketplace of death, thwarting the transfer of weapons, materials, and technologies. Proactive efforts like the Proliferation Security Initiative are great examples of the right kinds of efforts.

The United States must also demonstrate the willingness to defend itself. Missile defenses and a credible nuclear deterrent, combined with strong conventional forces that can do everything from rooting out an insurgency to striking an enemy's missile base deep inside its own territory, is the right answer.

Finally, America must be a nation prepared. Both the public and private sectors must work to ensure our resilience in the face of threats that could stop the heartbeat of the nation. The right approach is security, preparedness, response, and recovery solutions that will keep the nation safe, free, and prosperous in the face of catastrophic threats.

A World Without WMD

With a strategy focused on protecting and defending the nation, America can make a difference in the world. In the past, for example, Brazil, Libya, South Africa, South Korea, and Taiwan abandoned their nuclear weapons programs, and Russia slashed its weapons inventory. They did so not because of treaties and negotiations alone, but because the U.S. helped to set conditions that convinced them not to go nuclear. The U.S. has also worked with countries to voluntarily safeguard materials like highly enriched uranium or destroy threats such as chemical weapons.

The U.S. can and should play this role in the 21st century. It is in our own interests to do so. But to achieve success, we have to start with the right foundation-cooperative and non-cooperative efforts at threat reduction based on a strategy that shoulders the responsibility to protect and defend America.

James Jay Carafano, Ph.D., is Assistant Director of the Kathryn and Shelby Cullom Davis Institute for International Studies and Senior Research Fellow for National Security and Homeland Security in the Douglas and Sarah Allison Center for Foreign Policy Studies at The Heritage Foundation.