Two years ago last month in Prague, U.S. President Barack Obama put forward his visionary idea of a world free of nuclear weapons. A year ago, a new strategic arms treaty between Russia and the United States was signed in the same city. Now the worldwide wave of support for a full ban on nuclear weapons, or “nuclear zero,” is being transformed into a debate about nuclear deterrence. Indeed, the four American strategists who first called for nuclear zero — former U.S. Secretaries of State Henry Kissinger and George Shultz, former Defense Secretary William Perry and former Senator Sam Nunn — have partly backtracked and are now calling for an end to the doctrine of mutual assured destruction.

Unfortunately, their suggestions for accomplishing this are unclear. Their only concrete proposal is asymmetrical cuts of tactical nuclear weapons by Russia and the United States. But tactical weapons are not a serious threat to anybody. Moreover, Russia is not interested in reducing this part of its nuclear arsenal significantly. It needs such weapons to compensate psychologically for NATO’s preponderance — a reversal of the Cold War epoch — in conventional forces. More important, Russia considers these weapons insurance against the possibility of Chinese conventional superiority.

I firmly doubt the need to dispense with deterrence. After all, it worked successfully for decades. The unprecedented geostrategic, military and ideological confrontation of the Cold War never escalated into open, head-to-head warfare. The existence of nuclear weapons also curbed the conventional arms race.

The most important function of nuclear weapons during the Cold War — though little spoken of at the time — proved to be “self-deterrence.” Of course, each side considered itself peaceful and would not admit that it, too, had to be deterred. But the danger that any conflict could escalate into a nuclear confrontation prevented reckless and dangerous behavior on both sides on more than one occasion.

With communism’s collapse and Russia temporarily disabled, self-deterrence softened, and the United States ran off the rails as the global hyperpower. It behaved in ways that would have been unthinkable before — for example, its attacks on Yugoslavia, Afghanistan and Iraq. The latter two wars have been politically self-defeating for Washington, in addition to costing it trillions of dollars. The United States is no less militarily powerful now than previously, but it does not look so strong to the wider world.

Nuclear deterrence and mutual assured destruction would be passe only if we assumed that we — people, countries and humankind at large — had become so ideal and humane that we no longer needed self-deterrence. But, unfortunately, we are not such people, and nuclear weapons have played — and continue to play — a civilizing role in international relations. Their use would be so horrible that we tailor our behavior accordingly. As a result, we have little fear of World War III nowadays, even though unprecedentedly rapid changes in the global balance of power are creating classic conditions for unleashing it.

After all, the mere possession of nuclear weapons, even if aimed at each other, does not turn countries into enemies. Russian and Chinese strategists assume that part of their countries’ nuclear potential may be targeted at the other side. But this does not spoil their remarkable bilateral relations. On the contrary, it improves them. Russia, with its formal nuclear superiority, has no serious fears regarding China’s military buildup.

In this sense, nuclear weapons facilitate normal international relations, just like a good fence helps build good neighborly relations. Russia and the United States must seek to build relations such as now exist between Russia and China, Russia and France or among the United States, France and Britain.

Limited arms reductions might be useful for improving relations. But arms control talks are built upon the concept of the balance of forces, which is a sure recipe for reviving confrontational and militaristic thinking.

The talks on pan-European missile defense cooperation might come in handy. While missile defense is most likely unnecessary, given the absence of any serious threat, the administration of Obama and other U.S. realists — who are aware of the impossibility and uselessness of creating a nonpenetrable, multilayered missile defense system — need such talks. They must at least pretend that they intend to build it to appease the United States’ powerful nuclear isolationists, who long for the past golden age of U.S. strategic invulnerability.

Talk about creating regional, cooperative missile defense systems might be helpful in preventing the development of long-range missiles by Europe’s neighbors. It might also help Russia and the United States overcome their old habit of viewing each other as enemies.

But what is really needed is effective cooperation where it counts the most: containing the increasing instability in the greater Middle East, ensuring that Afghanistan does not turn into yet another regional cancer and preventing a chain reaction of nuclear proliferation in the region.

So far, only the United States and Russia — with the assistance, one hopes, of China, India, and the European Union — can hope to address these problems more or less effectively. They can offer security guarantees to responsible countries in the region. Sooner or later, peace will have to be imposed upon the Israelis and the Palestinians, who have proved to be incapable of reaching a settlement on their own.

Similarly, Russia and the United States need cooperation, not farcical rivalry, in developing new sea routes and possible energy deposits in the Arctic and in interacting with China and other Asia-Pacific countries in joint development of the resource potential of Siberia and Russia’s Far East. Russia will not be able to develop the region on its own. Developing it with China alone could prove to be a dangerous strategy.

But if the two countries fail to overcome their bad old habits of mutual suspicion, their remaining — and quite powerful — nuclear arsenals will continue to serve deterrence and self-deterrence. As long as we remain unable to make ourselves think and act in a civilized way, we can and must ensure that we do not become barbaric.