This paper, the text of a speech before the senior seminar of the Foreign Service Institute, Washington, D.C., November 14, 1991, comments on how the United States should approach national security, emphasizing the relationship between strategy and force structure. The dramatic events of 1991 have overturned some of the assumptions underlying policy decisions made in 1990 for the post-Cold War period. Today, for instance, it is hard to portray the Soviet Union and Iraq as serious military threats. The Defense Department and the executive branch thus may find it difficult to justify a continuing strong U.S. defense establishment without a readily identifiable and militarily powerful adversary. The national security community will have to develop an entirely new theory of U.S. policy, strategy, and forces for the post-communist era. To this end, the author makes six suggestions for assessing future U.S. military requirements: (1) address requirements "proactively," not passively; (2) relearn the art of thinking in terms of military strategy; (3) realize that the end of communism does not mean the end of international conflict; (4) maintain a long-term perspective; (5) remember that the Cold War was won by a sustained commitment to a worthy purpose; and (6) devise a coherent strategic concept for guiding defense strategy.