China has staged an impressive buildup of naval might. Like past newcomers to maritime competition—Imperial Germany and the Soviet Union, to name two—this historic continental power can now compete with the dominant sea power of the age. Indeed, its construction of an oceangoing fleet is skewing the balance of naval power in Asia against the United States and long-time allies such as Japan and South Korea. Within the China seas and much of the Western Pacific, moreover, China can supplement the striking power of its fleet with missiles, aircraft, and small naval craft operating from shore. This adds up to a potent challenge that the U.S. Navy must take seriously—lest it lose the maritime mastery on which America’s strategic position in Asia hinges.