Few analysts of U.S. involvement in Vietnam would agree with the provocative conclusion of this book. The thesis of most postmortems is that the United States lost the war because of the failure of its foreign policy decisionmaking system. According to Gelb and Betts, however, the foreign policy failed, but the decisionmaking system worked. They attribute this paradox to the efficiency of the system in sustaining an increasingly heavy commitment based on the shared conviction of six administrations that the United States must prevent the loss of Vietnam to communism. However questionable the conviction, and thus the commitment, may have been, the authors stress that the latter ""was made and kept for twenty-five years. That is what the system—the shared values, the political and bureaucratic pressures—was designed to do, and it did it."" The comprehensive analysis that supports this contention reflects the widest use thus fare of available sources, including recently declassified portions of negotiations documents and files in presidential libraries. The frequently quoted statement of the principals themselves contradict the commonly held view that U.S. leaders were unaware of the consequences of their decisions and deluded by false expectations of easy victory. With few exceptions, the record reveals that these leaders were both realistic and pessimistic about the chances for success in Vietnam. Whey they persisted nonetheless is explained in this thorough account of their decisionmaking from 1946 to 1968, and how their mistakes might be avoided by policymakers in the future is considered in the final chapter.