Like an imaginary friend in childhood, the Rapid Deployment Force (RDF may have helped America through a fearful time. Just one year ago, on March 1, 1980, President Jimmy Carter formally established the RDF to provide for quick military response to provocations anywhere in the world, but especially in the Persian Gulf. After a year of staggering problems -- interservice rivalry for control of the new organization, insurmountable shortcomings in airlift, sealift, communications, force availability and more -- the RDF is approaching a moment of truth. Reluctantly, the Reagan administration now verges on straightforward recognition of the fact that the RDF has held out a promise on which America's military cannot deliver.

In February 1981, in discussions culminating in recommendations to put the RDF under the European command, America's military tacitly reorganized that it would be difficult if not impossible to use elements of the RDF in the Southern Hemisphere, and in large portions of Asia, the Pacific and even the Indian Ocean. In plain truth, on a world-wide basis, the United States cannot on really short notice (days rather than weeks) deploy and support in action more than about a brigade -- 5,000 to 6,000 combat troops. According to the estimates of the RDF's own commanders, a force this size would face long odds in virtually any conceivable use.

From the first, the RDF has suffered from a lack of precision as to purpose. This has had nothing to do with the much overrated thought that a certain ambiguity about America's likely reponse actions. For political and practical reasons, the focus of the RDF has wavered. At its narrowest, the idea centered tightly on the potential need for military action in the Persian Gulf; at its fuzziest widening, the RDF concept implied an American intention to rebuild substantial worldwide interventionary capabilities. After the hostage-taking in Iran and the Soviet invasion of Afghanistan, many Americans seemed to desire assurances that the United States would defend citizens and interests against anything, anywhere, anytime. The RDF's problems of purpose reflect the collision of such septiments with sharp limitations on real military ability.

Now, with the hostages safely home and a new administration firmly in place, America may have an opportunity to outgrow this insubstantial but intimate companion. It is time to recall that the influence of great states does not depend on the rapidly with which they react to injury. Rather, influence depends on the certainty that, in good time and on good terms, great states redress wrong and reestablish rights. Modern empires, after all, grew to globe-straddling greatness in the leisurely age of sailing ships and infrequent mail.

In recent practice, Soviet leaders have shown considerable understanding of this element of influence. The Soviet invasion of Afghanistan was no spur-of-the moment affair; preparations for troop movements and other actions were in train for months before the invasion itself in December 1979. The methodical preparations seen to have preceded ultimate commitment have not noticeably diminished the world's respect for Soviet power, if not Soviet policies. Soviet preparations for possible action in Poland have been under way since the fall of 1980; it would be difficult to demonstrate that this has reduced. Soviet influence in Eastern Europe or beyond.

The RDF is not, and cannot become, an instantaneous answer to Irans and Afghanistans of the future. It is unrealistic to think the U.S. government can anticipate, prepare for and respond to all future injuries to citizens, interests or national pride. It is, perhaps, less unrealistic to hope the United States can improve its ability to safeguard well-defined interests in the Persian Gulf, given time and proper preparation.

But it is essential to recognize that a certain amount of political stability -- a working consensus on security interests, for a start -- will do for the United States what an RDF can never accomplish. For America needs the political constancy to act with deliberation, and not only to respond in passing moments of public outrage. In the forces it deploys, the United States needs clear objectives, sound prepration and high confidence of success much more than it needs rapidly.

The RDF may have been a good friend in 1980 to a nation troubled by problems it could neither solve nor ignore. But the RDF's first birthday should be its last. If America continues to rely on this fantastic friend, the nation will fail to mature toward a clear, effective coupling of its power to its policies.

Happy Birthday, RDF. Thank you. And goodbye.