To many Americans, the war in Vietnam was, and remains, a divisive issue. But nearly fifty years after the end of major U.S. combat operations in Vietnam, well over half the U.S. population is too young to have any direct memory of the conflict. The massive American commitment--political, economic, diplomatic, and military--to the mission of maintaining an independent and non-Communist South Vietnam deserves widespread attention, both to recognize the sacrifice of those who served and to remember how those events have impacted our nation.U.S. involvement in Southeast Asia began after World War II when elements of the Vietnamese population fought back against the re-imposition of French colonial rule. Although the United States generally favored the idea of an independent Vietnam, it supported France because the Viet Minh rebels were led by Communists and U.S. policy at that point in the Cold War sought to contain any expansion of communism. France's defeat in 1954 led to the division of Vietnam into a Communist North (Democratic Republic of Vietnam) and a non-Communist South (Republic of Vietnam). The United States actively supported the latter as it dealt with a growing Communist-led insurgent force (the Viet Cong) aided by the North Vietnamese. The initial mission of training South Vietnam's armed forces led to deepening American involvement as the situation grew increasingly dire for the Republic of Vietnam.By the time President Lyndon B. Johnson committed major combat units in 1965, the United States already had invested thousands of men and millions of dollars in the effort to build a secure and stable Republic of Vietnam. That commitment expanded rapidly through 1969, when the United States had over 365,000 Army soldiers (out of a total of a half million troops of all services) in every military region of South Vietnam, with thousands of other Army personnel throughout the Pacific area providing direct support to operations. The war saw many innovations, including the massive use of helicopters to conduct airmobile tactics, new concepts of counterinsurgency, the introduction of airborne radio direction finding, wide-scale use of computers, and major advances in battlefield medicine. Yet, as in most wars, much of the burden was still borne by soldiers on the ground who slogged on foot over the hills and through the rice paddies in search of an often elusive foe. The enormous military effort by the United States was, however, matched by the resolve of North Vietnamese leaders to unify their country under communism at whatever cost. That determination, in the end, proved decisive as American commitment wavered in the face of high casualties and economic and social challenges at home. Negotiations accompanied by the gradual withdrawal of U.S. forces led to the Paris Peace Accords in January 1973, effectively ending the American military role in the conflict. Actual peace was elusive, and two years later the North Vietnamese Army overran South Vietnam, bringing the war to an end in April 1975.The vast majority of American men and women who went to Vietnam did so in the uniform of the U.S. Army. They served their country when called, many at great personal cost, against a backdrop of growing uncertainty and unrest at home. This book, the twelfth volume of the U.S. Army's official history of the Vietnam War, is dedicated to them.