By John Lewis Gaddis, The Penguin Press, New York, N. Y., 784 pages, $39.95.

‘A dangerous man,” John Foster Dulles called George F. Kennan in 1950. Kennan, by then an experienced diplomat, had come out for the admission of Communist China to the United Nations. A new, authorized, prize-winning biography by Professor John Lewis Gaddis of Yale suggests that the real danger that Kennan posed was to the brand of Cold War diplomacy that Dulles preached and later came to practice.

The book provides a plethora of facts about every phase of the long, eventful life led by one of the most important diplomats of the 20th century. It also includes evaluations, not only the author’s and by no means always favorable, of Kennan’s ideas, outlooks, successes and failures. Whether or not the work qualifies as a definitive biography, it leaves little left to be said about its subject, who died in 2005 at age 101.

Kennan, a native of Milwaukee, joined the U. S. Foreign Service upon his graduation from Princeton in 1925. He gained a place in history when, as second-in-command at the Embassy in Moscow, he sent to Washington the celebrated “long telegram” of Feb. 22, 1946. In some 5,000 words he warned that the Soviet Union, so recently an ally in the struggle against Nazi Germany, must now be considered an ideological adversary and a geopolitical rival or even threat.

The “long telegram” had as its basis its writer’s years of study of Russian history, language and culture and his familiarity with Marxist-Leninist dogma. As Gaddis puts it, the telegram “became the conceptual foundation for the strategy the United States—and Great Britain—would follow for over four decades.”

A year or so later, Kennan elaborated on his telegram with an anonymous article, signed “X,” in Foreign Affairs. He called for “a policy of firm containment, designed to confront the Russians with unalterable counterforce at every point where they show signs of encroaching upon the interests of a peaceful and stable world.” Kennan’s anonymity did not last long. To this day, he remains identified as the originator of the Cold War policy of containment.

While George C. Marshall served as secretary of state, Kennan played a key role in Washington. He was appointed deputy commandant for foreign affairs at the newly-established National War College. As head of the State Department’s Policy Planning Staff, he participated in a multiplicity of crucial decisions, including the promulgation of the Marshall Plan. Late in 1948, however, President Truman named Dean Acheson to succeed Marshall. That succession marked the beginning of the end of George Kennan’s prominence in the formulation and administration of American foreign policy.

For more reasons than one, Acheson and Kennan did not get along. Most important, Kennan believed that the policy of containment was being misconstrued. He had not meant, he explained in later years, that containment should be practiced militarily. Rather, he argued, diplomatic and other pressures should be applied to resist Soviet expansion. Thus he opposed the Truman Doctrine, by which the United States undertook to bolster Greece and Turkey against communist aggression. He likewise dissented from the decision to form NATO.

The election of 1952, in which the people elected Dwight D. Eisenhower President, represented a further setback for Kennan. The Republicans had campaigned, with Dulles as their principal foreign-policy spokesman, for replacement of containment with “liberation.”

Four days before Eisenhower’s inauguration, with Dulles now a certainty as the next secretary of state, Kennan publicly denounced the new policy as “replete with possibilities for misunderstanding and bitterness.” Without naming names, he deplored “emotionalism, the striking of heroic attitudes and demagoguery of all sorts.” (Older readers will recall Winston Churchill’s appraisal of Dulles as “the only case of a bull I know who carries his china closet with him.”)

Thenceforth Kennan’s role in foreign policy became more and more one of observer and commentator rather than participant. He devoted increasing amounts of his time to lecturing, teaching and writing. Two of his books won Pulitzer Prizes for history. He spent years on the faculty of the Institute for Advanced Studies at Princeton.

By no means, however, did Kennan silence himself on the subject of foreign policy. He continued to complain of what he saw as misinterpretation of his policy of containment. He argued at one point, for example, that a withdrawal of U. S. troops from Europe might persuade the Soviet leadership of the absence of any danger of Western aggression. He complained of the “state of blind militaristic hysteria” that prevailed in the Reagan administration. He opposed American intervention in Vietnam and the campaign against Iraq.

Kennan’s years of duty in the Soviet Union and his intense studying of Russian history and culture had imbued him with a deep fondness for and respect of the Russian people. They did not, however, blind him to the realities of Soviet communism. He repeatedly condemned the Soviet state, once as “a regime of unparalleled ruthlessness and jealousy.”

A cosmopolite from boyhood, Kennan was not happy with his own country. He expressed disappointment with the shallowness and materialism of what he once referred to as “this thin, tight, lonely American life.”

The life of George F. Kennan is a life worth knowing more about. For lawyers, it is a life that teaches what can be accomplished by a total mastery of subject matter, by a refusal to be discouraged by obstacles and opposition and by the application of intelligence rather than emotion to a given problem. Professor Gaddis deserves praise and thanks for presenting that life in a scholarly and yet highly readable fashion.

Walter Barthold is retired from the practice of law in New York City.