KENNETH WALTZ served in the U.S. Army in World War II, became a ...leading proponent of realist “balance of power” theory during the Cold War, and has consistently maintained since then that new proliferators will also behave cautiously if they acquire the bomb. It is therefore not surprising to learn that Waltz fears that nuclear disarmament would “make the world safe for the fighting of World War III,” believes that the atomic bomb is the best “peacekeeping weapon” ever invented, and deduces that the Obama administration must, despite the president’s grand rhetoric, really have no intention of moving toward global zero. What is surprising is that Waltz exaggerates the peace-inducing effect of nuclear weapons, displays a strangely apolitical perspective on the causes of war, completely ignores the risks of nuclear terrorism and misrepresents Barack Obama’s statements about nuclear disarmament. Let me address these point by point.

Waltz claims that “states with nuclear weapons have never fought one another.” Wrong. India and Pakistan, after testing nuclear weapons in 1998, fought the 1999 Kargil War, in which over one thousand soldiers died. Moreover, the Kargil War occurred not despite Pakistan developing nuclear weapons but rather because Pakistan got the bomb. Pakistani generals thought that their new nuclear arsenal was a shield behind which they could safely sneak Pakistani soldiers into Indian-controlled Kashmir without triggering a war. They were wrong, dangerously wrong. And Waltz is wrong to ignore this history.

Waltz also notes that “even with the horrors of World War I fresh in their minds, European countries went into World War II.” This is apolitical political science. Didn’t Hitler and the Nazi Party’s ambition to create Lebensraum and gain mastery of Europe have something to do with the outbreak of war? Poland, England and France did not just stumble into war in 1939 and 1940. They were attacked by an expansionist power led by a megalomaniac leader who did not fear the consequences of war. (Indeed, by 1945 Hitler thought the German people should be destroyed because they had proven themselves unworthy of his leadership.) If the United States faced an aggressive leader like Hitler today, I would certainly advocate the maintenance of a U.S. nuclear arsenal for the sake of deterrence. But we do not now face that kind of threat in Russia and China. And the possibility of leaders like Iran’s Ahmadinejad getting nuclear weapons is precisely why the United States should work with others to pressure would-be proliferators and prevent the spread of nuclear weapons.

It is revealing that the word “terrorism” does not appear in Waltz’s essay. He may believe that terrorists’ interests in getting the bomb are exaggerated, or that governments can easily protect their arsenals from insider or outsider threats. But he is incorrect on both counts. Islamic jihadis, left-wing radicals and apocalyptic cults have all tried to get nuclear weapons. More proliferation will increase their chances of success. No wonder Waltz ignores this issue. He has no credible way to address it.

Waltz cites Obama’s Prague speech about America keeping nuclear weapons as long as others possess the same capability as evidence that we are not serious about disarmament. Wrong again. Obama was in fact emphasizing that the United States will not disarm unilaterally and that the process will take a significant amount of time. But if we can negotiate multilateral arms-reduction agreements and create new verification technology, safe and secure disarmament is possible. Waltz misinterprets Obama’s nod toward realism as hypocrisy.

Nuclear weapons have not been the best things since sliced bread. They have been a mixed blessing, a dangerous deterrent. The Cold War witnessed many close calls; new nuclear states will be even more prone to deterrence failures. Living with nuclear weapons was a perilous necessity in the past. It should not be repeated. Celebrating this dangerous condition is misguided.