Self-preservation and military measures to insure the territory of the United States against violation by foreign powers-the subject of this book-ceased to be of serious concern to the United States Government and nation during the nineteenth century. In World War I, the Americans concentrated on the offensive. In World War II, as the authors of this book remark, we passed to the offensive so soon and with such force after the United States became engaged that the military provisions for defense have been obscured from view. The authors focus on these measures and relate them to the evolution of American foreign policy in the period 1938-41. The experience acquired in preparing for defense when the danger of direct attack was regarded as constituting a state of emergency is one of great interest in our present state of danger when deterrence has become the policy of the nation and its armed forces.