Like many kids in the 80s, I was convinced I would die in a nuclear war. Dialogue between the United States and the Soviet Union had broken down after the Soviet invasion of Afghanistan. Ronald Reagan warned us that there was "a bear in the woods." Each side had many thousands of nuclear weapons pointed at the other, so that even if most of its arsenal were destroyed by a first strike it had enough to ensure the death of every person on the planet several times over. Television mini-series depicted life after a nuclear holocaust. And the Bulletin of Atomic Scientists set its "Doomsday Clock" to three minutes to midnight to suggest that it was the close the human race had yet come to destroying itself. The threat of "mutually assured destruction" hung over our heads.

The United States and Russia still have more than enough nuclear weapons to wipe out the human race. But with the end of the Cold War relations between the United States and Russia have thawed considerably, our ideological differences have receded into the background, and the threat of terrorism has replaced the threat of a nuclear confrontation in the popular imagination. Now that the danger of confrontation with Russia seems more distant, President Obama—who in Prague last year called for a "a world without nuclear weapons"—has decided to take "specific and concrete steps to reduce the role of nuclear weapons" in our national security strategy.

More than anything else, the change in our nuclear posture is a rhetorical move. Our "nuclear posture" is just that—a posture. The truth is that no matter what Obama or any President says, it's hard to believe that either that we would use strategic nuclear weapons in anything but fairly extreme circumstances, or that if the circumstances were extreme that we wouldn't consider using them. While they are often credited with keeping the Cold War from becoming a hot war—with bringing about a "nuclear peace" between the United States and the Soviet Union—they don't actually give us much political leverage in other contexts. We're not likely use them to resolve a trade dispute, and if we did use the threat a nuclear attack to pressure other countries, we'd instantly set the rest of the world—including the other nuclear powers—against us. At the same time, no statement of our nuclear policy will convince other countries that if we were truly threatened we wouldn't consider using a nuclear response. There's not really much leeway for the president to decide how we might use nuclear weapons.

But the change in tone matters. President Obama won't say that the United States would never use nuclear weapons first—and explicitly reserves the right to use them against rogue nuclear powers North Korea and Iran—but he does say we won't use them first against countries that have signed and are complying with the Non-Proliferation Treaty limiting the spread of nuclear weapons. As Fred Kaplan writes, in practice the main effect of this policy will be that we no longer target these countries. That gives other countries a greater incentive to adhere to the Non-Proliferation Treaty, and isolates countries like North Korea and Iran that don't. We'll begin to reduce the number of warheads our Minuteman missiles carry, which should reassure Russia that we are not considering a first-strike against them. And on Thursday Obama and Russian President Dmitri Medvedev will sign a new Strategic Arms Reduction Treaty (START) reducing the number of warheads each country can have by 30%.

That still leaves us an enormous stock of weapons, which we reserve the right to use. And, as White House Press Secretary Robert Gibbs points out, our conventional military forces are frightening enough to deter most attacks on their own. Nevertheless, it matters that we're no longer advertising the threat our nuclear arsenal poses. By changing our nuclear posture we're signaling our intention to work with—rather than simply threaten—other countries. In that sense, Vice President Biden may be right when he says the new policy "leaves cold war thinking behind."