State Department official George Kennan, using the pseudonym “Mr. X,” publishes an article entitled “The Sources of Soviet Conduct” in the July edition of Foreign Affairs. The article focused on Kennan’s call for a policy of containment toward the Soviet Union and established the foundation for much of America’s early Cold War foreign policy.

In February 1946, Kennan, then serving as the U.S. charge d’affaires in Moscow, wrote his famous “long telegram” to the Department of State. In the missive, he condemned the communist leadership of the Soviet Union and called on the United States to forcefully resist Russian expansion. Encouraged by friends and colleagues, Kennan refined the telegram into an article, “The Sources of Soviet Conduct,” and secured its publication in the July edition of Foreign Affairs. Kennan signed the article “Mr. X” to avoid any charge that he was presenting official U.S. government policy, but nearly everyone in the Department of State and White House recognized the piece as Kennan’s work. In the article, Kennan explained that the Soviet Union’s leaders were determined to spread the communist doctrine around the world, but were also extremely patient and pragmatic in pursuing such expansion.

In the “face of superior force,” Kennan said, the Russians would retreat and wait for a more propitious moment. The West, however, should not be lulled into complacency by temporary Soviet setbacks. Soviet foreign policy, Kennan claimed, “is a fluid stream which moves constantly, wherever it is permitted to move, toward a given goal.” In terms of U.S. foreign policy, Kennan’s advice was clear: “The main element of any United States policy toward the Soviet Union must be that of a long-term, patient but firm and vigilant containment of Russian expansive tendencies.”

Kennan’s article created a sensation in the United States, and the term “containment” instantly entered the Cold War lexicon. The administration of President Harry S. Truman embraced Kennan’s philosophy, and in the next few years attempted to “contain” Soviet expansion through a variety of programs, including the establishment of the North Atlantic Treaty Organization (NATO) in 1949. Kennan’s star rose quickly in the Department of State and in 1952 he was named U.S. ambassador to Russia. By the 1960s, with the United States hopelessly mired in the Vietnam War, Kennan began to question some of his own basic assumptions in the “Mr. X” article and became a vocal critic of U.S. involvement in Vietnam. In particular, he criticized U.S. policymakers during the 1950s and 1960s for putting too much emphasis on the military containment of the Soviet Union, rather than on political and economic programs.