Adverse Reactions Robert L. Gallucci As the world has become more multipolar over the last 75 years, so, too, have the nuclear threats to the United States. Today, China, North Korea, and Russia point their missiles, armed with thermonuclear warheads, at the American homeland. The task of extending nuclear deterrence to allies has also become more complicated for Washington. Those allies, including Japan and South Korea, are concerned that U.S. credibility is not what it once was and are now