CAN we head off nuclear war? With stakes in the 40-year rivalry growing more menacing and a new round of discussions with Russia just opening in Geneva in January, it is interesting to go back to George Frost Kennan, the man who first tossed off that curiously ambiguous and menacing word - ''containment.''
He has been studying Russia for almost 60 years and at one time was America's ambassador there. As a diplomatic historian he has written 16 books and won two Pulitzer prizes. Where do you place him? His views on world affairs infuriate the political left but, at the same time, he rejects the conservative Ronald Reagan concept of Russia as an ''evil empire.'' Some describe him as America's foremost authority on Russia. And yet he criticizes the Soviet view of the United States as ''neurotic'' with its ''dark suspicion of everything and everyone foreign'' and, on the other hand, feels Americans are going to extravagant lengths in their criticism of the Soviet Union.
Mr. Kennan, who has long since left government service, has recently become a key spokesman in the anti-nuclear war movement, including a recent collection, ''The Nuclear Delusion.''
In brief: He says nuclear weapons aren't a usable instrument for warfare.
Like others in a growing group, he considers them a suicide weapon. He joined with three other prominent former government officials, Robert S. McNamara, McGeorge Bundy, and Gerard C. Smith (respectively former secretary of defense, head of the National Security Council, and director of the Arms Control and Disarmament Agency). They urge the United States to pledge that it won't be the first to use nuclear arms.
But what good is that? The man in the street demands something more! Russia, it is argued, would use nuclear weapons if it came to a showdown. The observer on this imperiled planet has to agree to the risk. Soviet leaders have certainly pledged themselves publicly and repeatedly to the no-first-use policy. So what? There is another factor that Mr. Kennan and others increasingly note - there is a high possibility, indeed even a probability once nuclear arms are used, of escalation into general nuclear disaster.
World attention turns to this issue. Mr. Kennan (just before the Geneva conference) argues ''If we are not going to give up the option of first use and not slow down the arms race, then we have got to seek a political modus vivendi with the Russians that will reduce the danger of war. You cannot ask the people of Europe to sit indefinitely on the razor's edge. . . . We have got to come to some major understanding with the Russians which will permit a general relaxation of tensions. . . .''
A theory that Mr. Kennan adds to the discussion is the belief, after six generations of studying the Russians (in which he's yielded neither to a dogmatic pro- or anti-Russian side) that the ''Soviet leadership is much more defensive than aggressive.'' He looks back with distaste at what he still regards as manifestations of ''beastliness'' by the Russian heirarchy, but he is quoted as saying that the ''Soviet Union has changed profoundly since the death of Stalin in 1953. In that brutal dictator's place have come a succession of 'troubled men' - prisoners of the antiquated ideology to which their extreme sense of orthodoxy binds them. Their ambition is not to conquer, or even to convert the world but rather to keep their fragile empire together.''
Awed spectators here in Washington watch the preparations for a new attempt at Geneva to reach a formula with Moscow. Costs of armaments are at an all time global level and the dangers of nuclear war greater than ever. As explained in his commentary, Mr. Kennan, in his crusade against nuclear weapons, has turned not to the experts, with their imaginary and antiseptic scenarios of nuclear ''exchanges'' but to the public, whose inherent common sense he has previously questioned. Now he hopes the man in the street will intervene. He addresses himself to that public with a vigor intensified by what he sees as the urgency of the cause.
Mr. Kennan, the man who invented the term ''containment'' feels now the times are urgent, perhaps desperate.
Kennan, after these long years, sees the specter of nuclear war. He moves, says his biographer, because ''the danger to our civilization seems too horrifyingly clear to him, man's folly so obvious, the remedy so imperative.''