This book analyzes the establishment of an air defense identification zone (ADIZ) over the East China Sea in November 2013 by the People’s Republic of China (PRC, or China), international responses to that action, its consequences, and related matters of national interest and strategy. The book examines the legal, military, and diplomatic aspects of China’s ADIZ, with a focus on U.S. interests and issues of concern to Congress. It also discusses questions that have risen concerning the U.S. relationship with the Senkaku islets in the East China Sea; and the territorial claims in East Asia that underlie the growing tensions, U.S. interests that are at stake, factors that may be driving the growing tensions, and possible options for Congress to consider.