It was appropriate Tuesday that President Bush promoted the nation’s missile defense system at a Pennsylvania Boeing plant than manufactures the $40 billion V-22 Osprey vertical takeoff aircraft, which had design flaws that led to multiple crashes in 2000 and needed regular testing and retesting before the Pentagon said it was effective. The same will be true of the anti-missile program: If it is to work well enough to be trusted during times of emergency, its hit rate will have to improve and that will require more research.

President Bush, however, used the opportunity at the defense contractor to announce that those who wanted more proof before embracing the defense shield, first proposed in a different version 25 years ago, “don’t understand the threats of the 21st century.” The allusion was clearly toward his challenger, Sen. John Kerry, who, like a lot of members of Congress, wants to spend more on research for missile defense before buying the weapons system.

Last year, the General Accounting Office concluded, “Because of time pressures, MDA [the Missile Defense Agency] must include components that have not been demonstrated as mature and ready for system integration into a particular element, let alone the block overall … testing to date has provided only limited data for determining whether the system will work as intended in 2004.” Further, according the the GAO report, “MDA is beginning system integration of its first block with immature technology and limited testing. While doing so may help MDA meet the President’s deadline, it also increases the potential that some elements may not work as intended.”

Trying to figure out what sorts of wars the nation will fight in the 21st century is difficult. But on the cusp of the new century, in 1999, then-Secretary of Defense William Cohen explained on these pages, “The United States now faces something of a superpower paradox. Our supremacy in the conventional arena is prompting adversaries to seek unconventional, asymmetric means to strike our Achilles’ heel.” This means in addition to the worry about the potential of weapons of mass destruction in North Korea or Iraq, he said, the nation faces the threat that biological weapons “will find their way into the hands of individuals and independent groups – fanatical terrorists and religious zealots beyond our borders, brooding loners and self-proclaimed apocalyptic prophets at home.”

Prescient, and his thoughts were echoed by Sen. Kerry in May 2001: “Missile defense will do nothing to address what the Pentagon itself considers a much more likely and immediate threat to the American homeland from terrorists and from nonstate actors, who can quietly slip explosives into a building, unleash chemical weapons into a crowded subway, or send a crude nuclear weapon into a busy harbor.”

No one in this country is more aware of that than President Bush, and no matter how large the defense budget, it is not infinite, so choices about what sort of protection is most necessary must be made.

Accusing anyone who concludes missile defense is not a mature technology of failing to face the current reality doesn’t address the real question. The question is this: What is the most pressing threat for which this nation is least prepared? A lot has changed since Sept. 11, but the answer to that question has not.