The second half of the 20th century featured a strategic competition between the United States and the Soviet Union. That competition avoided World War III in part because during the 1950s, scholars like Henry Kissinger, Thomas Schelling, Herman Kahn, and Albert Wohlstetter analyzed the fundamental nature of nuclear deterrence. Decades of arms control negotiations reinforced these early notions of stability and created a mutual understanding that allowed U.S.-Soviet competition to proceed without armed conflict. The first half of the 21st century will be dominated by the relationship between the United States and China. That relationship is likely to contain elements of both cooperation and competition. Territorial disputes such as those over Taiwan and the South China Sea will be an important feature of this competition, but both are traditional disputes, and traditional solutions suggest themselves. A more difficult set of issues relates to U.S.-Chinese competition and cooperation in three domains in which real strategic harm can be inflicted in the current era: nuclear, space, and cyber. Just as a clearer understanding of the fundamental principles of nuclear deterrence maintained adequate stability during the Cold War, a clearer understanding of the characteristics of these three domains can provide the underpinnings of strategic stability between the United States and China in the decades ahead. That is what this book is about.