In the midst of these developments, Kennan began working on an essay for the journal Foreign Affairs that was meant as a formal version and elaboration of his Long Telegram. But he was pulled away by an assignment from Secretary of State George C. Marshall to come up with a plan for postwar European reconstruction. The Marshall Plan was subsequently announced in June, 1947. Its intent was to rejuvenate Western Europe and the Mediterranean in order to serve as a bulwark against Soviet expansion.

By July, 1947, when Kennan, writing under the anonymous name of Mr. X (because he was about to become the first head of the State Department’s policy planning staff), published his famous article in Foreign Affairs, entitled “The Sources of Soviet Conduct,” the Cold War was already up and running, with the United States actively taking steps to halt further Soviet expansion. In the article, Kennan bore down on his theme from the Long Telegram, emphasizing that the Soviets recognized “no restrictions, either of God or man, on the character of their methods.” Yet, partly because of Russian history and partly because the Soviets’ very methods were bound to produce a backlash, they would never feel secure.

Nevertheless, as Kennan went on in his Foreign Affairs article, “The theory of the inevitability of the eventual fall of capitalism has the fortunate connotation that there is no hurry about it.” As Kennan’s biographer John Lewis Gaddis put it: “Like the church, the Kremlin could afford to wait.” Moreover, as Kennan went on, because the Soviet system “bears within it the seeds of its own decay … a policy of containment,” in which the United States competed with the Soviet Union for influence throughout the world might eventually, given enough time, prove successful. But Kennan did not rule out that containment at some point might involve a military conflict with the Soviet Union itself. Containment was not necessarily a wholly peaceful doctrine. Indeed, Kennan wrote of “firm containment” employing “unalterable counter-force at every point.”

Reader’s Digest and Life printed excerpts of the Mr. X article. Kennan was famous. His idea of “containment,” utilized as a grand strategy, was the roughest of guides only. Kennan himself at this nascent stage of the Cold War was even ambivalent about whether it would include military force or not against the Soviet Union. And some of the biggest moves in the Cold War that were to come—the CIA-instigated coups in Iran and Guatemala, the Vietnam War—were policy actions that Kennan would come to deeply regret. And Kennan’s article in Foreign Affairs did not completely lead the way, as both the Truman Doctrine and the Marshall Plan came about before the article was even published, though Kennan had played a very significant role in their formulations.

Most crucially, containment arose out of negatives: out of what a consensus of the inner circle of policymakers had agreed would not work. As Walter Isaacson and Evan Thomas imply in The Wise Men: Six Friends and the World They Made, Charles Bohlen and Dean Acheson more-or-less agreed that going to war against the Soviets—or, at the other extreme, retreating into isolationism—were simply not viable. Such policies would not, in any case, gain support from an American public, which, following World War II and the sacrifices it entailed, were tired of military conflict; yet, also because of the war and the dispatch of millions of men and women to Europe and Asia, the American people understood that the United States had a vigorous role to play in international affairs. Containment was an obvious middle path: through diplomacy, foreign aid, and the movement of troops and warships, limit or contain Soviet expansion. Wait them out, in other words, since their system at heart was more brittle than America’s.

KENNAN’S CONCEPT was brilliant. Especially in politics, very few ideas, after all, are completely original, and many good ideas emerge from what is, in fact, obvious. It is just that a good theorist sees more clearly what is obvious than others do. Kennan had clearly become the master of grand strategy. But as we shall see, grand strategy, even when successful, can provide little direction when it comes to making one searing decision after another over decades.

Most philosophers and theorists are sooner or later misunderstood, and their ideas become bowdlerized. Kennan felt that this is what happened to containment. In a word, he had meant to inject more nuance into his Long Telegram and Foreign Affairs article, and therefore was a bit shocked when they were used as ammunition for defending a particular hardline strategy against the Soviets. For example, Walter Lippman wrote fourteen columns for the New York Herald Tribune about the X article, proclaiming that Kennan had created a “strategic monstrosity” that would exhaust the United States and force it to rely on a ramshackle assemblage of weak and disorderly states in order to compete with the Soviet Union. By the late 1940s, however, Kennan had come to assess that negotiating and living in peaceful coexistence with the Soviet Union was possible. There was a myriad of other choices and details to be worked out besides war with the Soviet Union at one extreme and appeasement of it at the other. And containment offered not that much of a guide as to what those other choices were. Significantly, Kennan saw the possibility of a change in Soviet behavior. When the Korean War suddenly broke out in 1950, Kennan worried about “the militarization of thinking” that was now taking place, which would make “any discriminate estimate of Soviet intentions” on our part “unwelcome and unacceptable.”

Indeed, Kennan’s original idea was so broad that in the course of the Cold War it would become subject to different interpretations. For example, whereas Kennan is today lionized by the liberal foreign policy establishment while Dwight D. Eisenhower’s secretary of state, John Foster Dulles, is often disparaged by that same liberal establishment as having been too hardline (associated as Dulles is with the CIA-sponsored coups in Iran and Guatemala), Dulles was merely applying containment as he had understood it.

Because containment was so broad, Kennan himself got big things wrong. He was opposed to the creation of West Germany, which he believed would become a stage-set for German nationalism and irredentism. Such a state, he said, would “be neither friendly nor frank nor trustworthy from the standpoint of the Western occupiers.” Of course, West Germany turned out to be exactly the opposite: for decades carving out a role as stable, friendly, trustworthy, and dedicated to submerging German national identity within an embryonic pan-European identity.

As Kennan and West Germany demonstrate, even the most successful grand strategy in modern history does not provide answers to everything or even to most things. Moreover, it does not guard against mistakes, blunders, bloody and misbegotten wars, and plain bad judgement. Containment served America well. It was better than nuclear war or isolationism. But the history of America’s involvement in the Cold War is, nevertheless, one punctuated with tragic mistakes. That is not the fault of containment. Grand strategy of even the best sort has severe limits.

NINE PRESIDENTS, from Harry Truman to George H.W. Bush, navigated the United States through the treacherous waters of the Cold War. Kennan’s containment strategy would emerge triumphant at the end, with the ascent of a Soviet leader who saw with penetrating clarity the decrepitude of the system he had inherited, and, in seeking to reform the system, actually ended up dismantling it—thus bringing an armed truce of forty-four years in Central Europe to a peaceful conclusion. Yet, for long periods between Stalin’s speech at the Bolshoi Theater and the collapse of the Berlin Wall, the concept of containment receded into near-invisibility as one American president after another agonized over wars and other nerve-wracking crises. Containment was so broad a guide that in the crucible of decisionmaking it was barely a guide at all. It was organized common sense at the most elemental level. And common sense, even when organized, does not always prevail. Passion, intrigue, and other Shakespearean factors, in addition to competing visions of common sense itself, often get in the way.

Though the Cold War began with Stalin’s speech and Soviet threats against Iran and the eastern Mediterranean—and accelerated with the Communist victory on mainland China—from the viewpoint of the American public the Korean War was the first truly bloody and memorable event. On January 12, 1950, at the National Press Club in Washington, Truman’s secretary of state, Dean Acheson, included Japan and the Philippines inside the U.S. defense parameter in Asia but did not explicitly include South Korea. As the Washington conventional wisdom went, South Korea was not necessarily a vital chess piece, nor was it seen to be in unequivocal danger. Containment, as a general principle, provided no exact answer to this question. Yet, as the historian James L. Stokesbury writes, “It was one thing to decide rationally that South Korea was not vital to American interests. It was quite a different thing to watch it sink before a tide of Communist invasion” when 100,000 North Korean troops, supported by Stalin, crossed the 38th parallel into South Korea on June 25. “The [American] government that had ‘lost China’ had to do something…”