This manual, Army Doctrine Publication ADP 3-28 Defense Support of Civil Authorities July 2019, is the doctrinal foundation for the Army’s contribution to defense support of civil authorities (DSCA). ADP 3-28 explains how the Army conducts DSCA missions and National Guard civil support missions as part of unified land operations. ADP 3-28 focuses on achieving unity of effort among the Army battalions, brigades, division headquarters, and Army Service component commands conducting DSCA with support from the institutional force and in cooperation with joint and interagency partners.

The principal audience for ADP 3-28 is all members of the Army profession. Commanders and staffs of Army headquarters serving as joint task force headquarters should also refer to applicable joint doctrine concerning the range of military operations and joint forces. In addition, trainers, educators, and contractors throughout the Army will also use this publication as a doctrinal reference. United States Pacific Command and United States Northern Command conduct DSCA within their respective areas of responsibility. Users in United States Pacific Command should refer to theater plans and procedures for DSCA.

ADP 3-28 clarifies similarities and differences between defense support of civil authorities (DSCA) and other elements of decisive action. DSCA and stability operations are similar in many ways. Both revolve around helping partners on the ground within areas of operations. Both require Army forces to provide essential services and work together with civil authorities. However, homeland operational environments differ from those overseas in terms of law, military chain of command, use of force, and inter-organizational coordination among unified action partners. This ADP helps Army leaders understand how operations in the homeland differ from operations by forces deployed forward in other theaters. It illustrates how domestic operational areas are theaters of operations with special requirements. Moreover, this ADP recognizes that DSCA is a joint mission that supports the national homeland security enterprise. The Department of Defense conducts DSCA under civilian control, based on U.S. law and national policy, and in cooperation with numerous civilian partners. National policy, in this context, often uses the word joint to include all cooperating partners, as in a joint field office led by civil authorities.