PARIS — It is, I suppose, too discouraging to face the fact that in international affairs (and indeed in national affairs; but that is another subject) paradox and contradiction rule the world. Policymakers and politicians consistently get what they don’t want.

Wars of aggrandizement end up failing to produce the expected gains — their geographical aims, or projected seizure and control of foreign resources, or augmentation of their power (whether soft or hard).

A reason for such national failures is unwillingness or inability to admit (often even to themselves) their real motives. Nations certainly do not admit these to the international audience. I am not talking about refusal to admit that an attack on another country is motivated by the wish to seize its oil or uranium or rare earths. I mean the secret or suppressed or sometimes even subconscious motives of governments.

Wars of defense more often than not are motivated by illusion or fantasies that disguise real or sublimated aggression. Many wars are the product of entangled motives that include such aggressive ambitions and fears — often unwarranted, but deliberately exaggerated for aggressive reasons and propaganda.

The United States provides one convenient, indeed irresistible, current case of self-deception. The war being promoted in the United States against Iran is (or would be) a war of aggression disguised, by but also to the leaders themselves, as a preventive war necessitated by threat — as if an Iran in possession of nuclear weapons would perform so suicidal an act as to attack the United States, or more to the point, Israel.

The real motive for Israel to attack Iran would be to destroy a medium-sized hostile power, not because Iran is a nuclear threat, but because, even without nuclear armaments, Iran by its size, history, resources and economic potential is a serious competitor to Israel in a region that is itself hostile to Israel and the United States. One cannot say inherently hostile, since Jews since the 8th century lived on reasonably peaceful terms in Islamic-ruled societies, ended only in the 20th century with the partition of Palestine. In fact, Jews and Arabs both lived more peacefully with one another in the Maghreb and Middle East than either did in the past with Christian Europe. So a preventive destruction, or crippling, of modern Iran may seem merely a brutal but useful precaution to Jerusalem (or Washington), but in the long run could have enduring historical consequences.

The United States would in such a case not simply be acting in response to the political stranglehold Israel now enjoys over the majority of members of the U.S. House of Representatives and much of the Senate, or because of the American formal alliance with Israel. It would be going to war with Iran to serve one of its permanent if unacknowledged foreign policy objectives: the preservation of as much as possible of its surviving quasi-monopoly of global nuclear military power.

Pakistan, India and now North Korea acquiring nuclear weapons is bad enough. But Washington’s interest is to stop as many as possible of the other candidates for nuclear weapons from obtaining them — to preserve an already broken American nuclear monopoly. To attempt this is illusion, in the longer run a futile effort. Nuclear proliferation is already so extensive that the U.S. cannot halt it.

Germany in 1914 wanted hegemony in Europe, a neutered France and a navy sizable enough to limit the freedom of action of the British Royal Navy. It actually got its own destruction, a damaged but victorious Franco-British alliance, the (temporary) end to American isolationism, dismantlement of its ally, Austria-Hungary, and a radicalized Russia with global revolutionary designs. Its had been a self-defeating ambition.

Germany’s search for revenge after 1918 gave Europe Nazism, the Second World War and all the other horrors that we already know too well.

What are China’s real ambitions, now that President Obama has “pivoted” to East Asia? For the present, probably limited ones, which have already been implicitly declared: notably to re-establish China’s historic position as the “middle kingdom” in East Asia with its smaller neighbors accepting tributary roles. With skillful diplomacy, this possibly could be accomplished. Much would depend on Japan (in modern history, China’s challenger), Korea (united or otherwise) and Taiwan.

This would amount to the relationship among these states that existed before American intervention in what was until the late 19th century an isolated, “hermit” Japan, and before large-scale intervention in China by British and European imperialism. This was also an East Asia that had not encountered modern nationalism, modern ideology, modern technology and global capitalism.

As I have warned before, and as domestic events in China during the past year have confirmed, that great and powerful civilization must come to terms with its past, particularly with the horrors of its Maoist past. It must do as Mikhail Gorbachev forced Soviet Russia to do: to tell itself the truth about its history and about the present legacy of that history. China may not be fortunate enough to find a Chinese Gorbachev, and a Chinese glasnost.

The Obama administration in Washington seems convinced that it (and its successors) can and should play a role in the current and future evolution of this Asia. It already has a complex of intertwined economic and commercial interests in the region, which is fine. A political or military role is not fine. This is the time for Americans to examine which of their true national interests are involved in East Asia, define them clearly to themselves, and, to the best extent possible, resist any temptation to profit from the troubles that may come. It certainly does not need still another war.

Visit William Pfaff’s website for more on his latest book, “The Irony of Manifest Destiny: The Tragedy of America’s Foreign Policy” (Walker & Co., $25), at www.williampfaff.com.