The surprise Chinese invasion of Vietnam in 1979 shocked the international community. The two communist nations had seemed firm political and cultural allies, but the twenty-nine-day border war imposed heavy casualties, ruined urban and agricultural infrastructure, leveled three Vietnamese cities, and catalyzed a decadelong conflict. In this groundbreaking book, Xiaoming Zhang traces the roots of the conflict to the historic relationship between the peoples of China and Vietnam, the ongoing Sino-Soviet dispute, and Chinese leader Deng Xiaoping's desire to modernize his country. Deng's perceptions of the Soviet Union, combined with his plans for economic and military reform, shaped China's strategic vision. Drawing on newly declassified Chinese documents and memoirs by senior military and civilian figures, Zhang takes readers into the heart of Beijing's decision-making process and illustrates the war's importance for understanding the modern Chinese military, as well as China's role in the Asian-Pacific world today.