The role of the military on U.S. soil is frequently misunderstood when it comes to the question: Who is in charge? This generally stems from confusion over the different homeland oriented missions: homeland security, homeland defense, and defense support of civil authorities.

The lack of guidance in this area prompted Bert Tussing, professor of national security affairs at the U.S. Army War College, and Dr. Robert McCreight to publish a new book, Introduction to Homeland Defense and Defense Support of Civil Authorities: The U.S. Military Role to Support and Defend. In a discussion led by Heritage’s Steven Bucci on February 3, Mr. Tussing expressed optimism that a better understanding of this role will help promote an “air of cooperation, rather than competition.”

Homeland defense is a primary responsibility of the Department of Defense (DOD) and can be most easily defined as the military “protection of U.S. sovereignty, territory, domestic population and critical defense infrastructure against external threats and aggression.” Homeland security is primarily, but not exclusively, the responsibility of the Department of Homeland Security and is intended to minimize or reduce U.S. vulnerability to a threat or hazard, minimize and respond to the consequences of an attack or disaster, and conduct other government functions ranging from law enforcement at special events to border security. Depending on the scope and type of threat or circumstances facing the U.S., the DOD may contribute resources and capabilities in support of the civilian homeland security mission. This support generally follows requests for assistance or a Presidential Disaster Declaration in the absence of adequate civilian resources and response capabilities and is referred to as Defense Support of Civil Authorities.

Despite what these definitions suggest, military support should not be viewed only as a last resort or as a resource bank to be tapped into when state and local resources have been exhausted. The military can provide preemptive and critical assistance in planning a response to major disasters and emergencies but only if a working relationship is established prior to a disaster declaration.

According to Mr. Tussing, planning is the “mother’s milk” of military core competencies. This is a strength that can be leveraged if the resources and capabilities of homeland defense and defense support for civil authorities are understood.

Rachel Zissimos is currently a member of the Young Leaders Program at The Heritage Foundation. For more information on interning at Heritage, please click here.