The application of our Armed Forces within the states and territories of the United States is far from intuitive. The challenges of defending the country against assaults within the homeland are much more complex than engaging our enemies on foreign soil. Likewise, the introduction of the military’s appreciable capabilities in response to disasters, be they natural or manmade, comes with authorities and restrictions reflective of an American ethos that will always hold those forces as the servants of the people, never their overseers. Introduction to Homeland Defense and Defense Support of Civil Authorities (DSCA): The U.S. Military’s Role to Support and Defend examines the requirements and regulations that guide the utilization of our forces in the domestic environment.