Army Doctrine Publication (ADP) 3-28 describes a doctrinal foundation for the Army's contribution to defense support of civil authorities (also called DSCA) (see figure 1, page iv, for a graphical overview). ADP 3-28 focuses on the operational Army battalions, brigades, division headquarters, and Army Service component headquarters conducting DSCA, with support from the generating force. A corresponding Army doctrine reference publication (ADRP) elaborating on the principles in ADP 3-28 is expected to replace Field Manual (FM) 3-28. The principal audience for ADP 3-28 is all members of the profession of arms. Commanders and staffs of Army headquarters serving as joint task force or multinational headquarters should also refer to applicable joint or multinational doctrine concerning the range of military operations and joint or multinational forces. Trainers and educators throughout the Army will also use this publication. Commanders, staffs, and subordinates ensure their decisions and actions comply with applicable United States, international, and, in some cases, host-nation laws and regulations. Commanders at all levels ensure their Soldiers operate in accordance with the law of war and the rules of engagement. (See Field Manual [FM] 27-10.) ADP 3-28 applies to the Active Army, Army National Guard/Army National Guard of the United States, and United States Army Reserve unless otherwise stated. ADP 3-28 does not apply to certain Army organizations and activities that support civil authorities or emergency response. First, state Army National Guard support in state active duty status falls outside the definition of DSCA. Second, ADP 3-28 does not address domestic counterterrorism operations. Third, it does not apply to any state defense force or equivalent that is not part of a state's National Guard. Fourth, ADP 3-28 does not apply to military activities conducted wholly within any military installation in the United States. Finally, it does not apply to the United States Army Corps of Engineers (USACE) although USACE plays a significant role in DSCA. United States Pacific Command (USPACOM) and United States Northern Command (USNORTHCOM) conduct DSCA within their respective combatant commands. This ADP uses terminology and methods universal to DSCA. Users in USPACOM should refer to theater plans and procedures for DSCA.