"Exactly twenty-five years from 1 May 1950- the day President Truman authorized the first U.S. military assistance to Indochina- Saigon and the South Vietnamese government fell to the communist regime of North Vietnam, on 30 April 1975. Thus ended the longest conflict in American history. After every prolonged conflict in its experience, the United States has plunged into a period of assessment, trying to sift out the meaning of the memorable events of the recent past while searching for the key to a conflict-free future. This happened in the 1870s after our Civil War, in the 1920s after World War I, and for a relatively brief period in the late 1940s after World War II. But with the advent of the Cold War in 1947, followed by the Korean War in 1950- our first experience with limited war- we lived through over a quarter of a century during which the United States was continuously involved in some sort of emergency, contingency, or actual hostilities somewhere in the world. And so, after our agonizing experience in Vietnam, the first clear failure in our history, it is not surprising to find the United States of the 1970s and 1980s brooding over its frustrations and reevaluating its role in the world."