Nuclear weapons have posed the heaviest burden of leadership for every American president since Harry Truman. There can be no more awesome responsibility than having to think about the circumstances under which a nation or perhaps even the world would be destroyed on your command, as George W. Bush has just been reminded.

The classified version of this administration's first important statement to itself about nuclear weapons found its way into the Los Angeles Times last weekend. The disclosure provoked outcries of alarm from anti-nuclear activists and a determined effort by officials to minimize or dismiss the document.

Don't buy the smoke screen. The nuclear posture review written at Donald Rumsfeld's Pentagon is a revealing statement. This planning document helps establish an ethos of nuclear strategy that will inevitably influence what and how the president thinks about atomic weapons.

Ronald Reagan was horrified by his first detailed briefing on American nuclear strategy, according to a famous story told by his aides. Reagan was so revolted by the doctrine of mutual assured destruction (MAD) and its balance of terror that he demanded an alternative: a strategic defensive shield against Soviet nuclear attack. The idea collapsed along with the Soviet Union.

Reagan's emotional response to the ultimate weapon resembled the nuclear antipathy expressed by Jimmy Carter and Bill Clinton during their presidencies. A calculated, highly pragmatic approach seems to characterize the Presidents Bush, father and son.

I found candidate George W. Bush's campaign discussions of nuclear strategy to be careful to businesslike. In his initial exposure to the grim details of how much destructive power he would have at his fingertips, Bush posed a deceptively workaday question: Why do we need so many nuclear weapons now that the Soviet Union has disappeared?

The Soviet attack on Europe that U.S. nuclear weapons were to deter had lost all plausibility in Bush's mind. He prodded discussions about unilateral reductions in the U.S. arsenal that would save money and perhaps contribute to better relations with Russia. His version of missile defense is far more tentative and far less ideological than was Reagan's Star Wars notion. When the Russians insisted on a legally binding document to cover strategic arms reductions, Bush went along.

So there was little theology or Strangelovian analysis in Bush's original contemplation of nuclear strategy. Then came Sept. 11 and the war in Afghanistan. Those events have significantly darkened this administration's nuclear ethos. Any weapons that can be used to preempt worst-case scenarios are being looked at in a new light.

This is one of the three important indirect revelations of the nuclear posture review: It suggests that deterrence is a meaningless concept for suicidal terrorists like Mohamed Atta and probably for Osama bin Laden and al Qaeda. That may be true for Iraq's Saddam Hussein or North Korea's Kim Jong Il as well. The review makes clear a turn by the Bush team to a strategy of preemption, including by nuclear weapons if necessary, to prevent these rulers from passing on weapons of mass destruction (WMD) to terror networks. This represents a devaluation of deterrence by the Bush administration.

Second, the authors of the defense paper document the administration's deepening skepticism about the effectiveness of traditional U.S. and international nonproliferation policies and arms control treaties.

Thinking they were talking in private, the planners list seven countries as candidates to glow in the dark permanently if they get out of line: Russia and China, because of the size of their arsenals and the uncertainty of their political futures; Iraq, Iran and North Korea, performing "axis of evil" encores here because they support U.S.-targeted terrorists and have or seek WMD; Libya and Syria, not previously spotlighted but secret makers and stockpilers of chemical weapons.

Finally, like most bureaucratic exercises, the paper works backward from a desired conclusion. The goal is a resumption of nuclear testing. The authors sing the praises of new mini-nuclear weapons and radioactive bunker-busters that, alas, cannot be developed if the United States continues the voluntary moratorium on testing being observed by the world's established nuclear powers.

That, for me, is the least convincing part of the exercise. The losses from going first and thereby encouraging China or France to test new nuclear devices outweigh the gains that a resumption of U.S. testing now would bring. And it would do nothing to lessen Bush's Toxic Texan image abroad.

The administration is right in insisting that this is the beginning, not the end, of an important internal discussion. But it is being intellectually dishonest in disowning the shaping power of what has already been written and which must now be weighed by the president.