This field manual provides direction for the corps headquarters: what it looks like, how it is organized, how its staff operates, how it is commanded and controlled, and how it operates in full spectrum operations. This publication replaces the previous edition of the Army's corps operations manual and describes the organization and operations of the corps. It reflects current doctrine on the elements of full spectrum operations: offense, defense, and stability or civil support. This manual addresses these elements without regard to priority. This manual: Incorporates the Army's operational concept, full spectrum operations; Describes the stand alone corps headquarters; Links brigade combat team and division doctrine with theater army doctrine. It describes the principles underlying the Army modular corps; Shows a corps headquarters designed for four primary employment roles-in priority-an Army intermediate tactical headquarters, an ARFOR, a joint force land component command headquarters, and a joint task force headquarters; Recognizes that the corps headquarters normally requires augmentation with elements from theater-level organizations for selected missions; Discusses when serving as a joint task force or joint force land component command, the corps may require a separate subordinate headquarters to serve as the ARFOR or may need augmentation to serve as both the joint headquarters and the ARFOR; Introduces a staff organization that reflects the warfighting functions discussed in Field Manual (FM) 3-0; Describes the three designated command and control facilities: main command post, tactical command post, and mobile command group; Describes the ability of the corps headquarters to readily accept joint augmentation from a standing joint force headquarters core element or other joint manning and equipping source.