This book explores the question “Why is the US Navy in the South China Sea at all?” It traces the history of diplomatic, economic, and military tensions among the People’s Republic of China, the Soviet Union, the United States, and the Socialist Republic of Vietnam, outlining the origins of the United States-Vietnam relationship during the immediate post-World War II period, the turmoil of the Vietnam War during which China supported North Vietnam against a US-backed South Vietnam, and the decision of the US government to open relations with China beginning in 1972. It shows how from 1945–1975, the US government used its relations with Vietnam to exert diplomatic, economic, and military pressure on China to open negotiations leading to full recognition and further discusses the surprising action of the US Navy in 1974 to allow the Chinese Navy to take the Paracel Islands by force, thereby denying control over these islands to a united Vietnam, closely allied with the Soviet Union, which was the common enemy of both China and the USA. Overall, the book demonstrates how the presence of the US Navy in the South China Sea is a crucial element in much wider, global US strategy.