Defense Primer: Department of the Army and Army Command Structure

Defense Primer: Department of the Army and Army Command Structure

Defense Primer: Department of the Army and Army Command Structure

Updated December 8, 2025 (IF10544)

Overview

Article I, Section 8, of the Constitution stipulates, "The Congress shall have power ... to raise and support Armies ... make Rules for the Government and Regulation of the land and naval Forces ... for calling forth the Militia to execute the Laws of the Union, suppress Insurrections and repel invasions."

The Department of the Army (DA) is one of three military departments, along with the Navy and Air Force, reporting to the Department of Defense (DOD), which is using "Department of War (DOW)" as a "secondary title" under Executive Order 14347, dated September 5, 2025. The Army's primary mission is to fight and win the nation's ground wars. The Army is composed of four distinct components: the regular Active Component (AC), the reserve components of the United States Army Reserve (USAR), the Army National Guard (ARNG), and Department of the Army civilians (DAC). See Table 1.

The Regular Army is the full-time, federal force of AC soldiers.

USAR is a federal reserve force that provides specialized units and capabilities, as well as individual soldiers when mobilized.

ARNG is a dual-status force that normally remains under the command of state governors and can respond to domestic emergencies, unless its units are mobilized for a federal mission.

DAC are federal government workers who fill a variety of support roles.

Table 1. Army Components

Component

Total
Number

Location
(CONUS/OCONUS)

AC

448,276

396,586 / 51,690

USAR

170,601

163,262 / 7,339

ARNG

328,084

316,742 / 11,342

DAC

223,386

212,364 / 11,018

Source: Defense Manpower Data Center, as of June 30, 2025.

Note: CONUS = Continental United States and OCONUS = Outside of the Continental United States (overseas).

Army Senior Leadership

The Department of the Army is led by a civilian Secretary of the Army appointed by the President with the advice and consent of the Senate. The Secretary of the Army reports to the Secretary of Defense, who is using "Secretary of War" as a "secondary title" under Executive Order 14347, dated September 5, 2025, and serves as civilian oversight for the Army and Chief of Staff of the Army (CSA). The CSA is an administrative position held by a four-star Army general and is a statutory office (10 U.S.C. §7033). The CSA is the chief military advisor and deputy to the Secretary of the Army and, by statute (10 U.S.C. §151), serves as a member of the Joint Chiefs of Staff (JCS). The JCS is composed of DOD's (DOW's) senior uniformed leaders who advise the President, Secretary of Defense (War), and Cabinet officials on military issues.

Command Authority

The Secretary of the Army's and the Chief of Staff of the Army's authorities are prescribed by law: 10 U.S.C. §7013 for the Secretary of the Army and 10 U.S.C. §7033 for the Chief of Staff of the Army. The CSA does not have operational command authority over deployed Army units. Under 10 U.S.C. §162, the operational chain of command runs from the President to the Secretary of Defense (War) and then to the commanders of the unified combatant commands, with the Chairman of the Joint Chiefs of Staff (CJCS) serving as the principal military advisor rather than a commander of forces. The CSA does, however, exercise supervision of Army units and organizations as designated by of the Secretary of the Army.

Operational and Institutional Missions

The operational Army—known as the Operational Force—conducts or directly supports military operations and consists of numbered armies, corps, divisions, brigades and battalions. The majority of the Army is based in the continental United States (CONUS) relying on forward-stationed and rotational units outside the continental United States (OCONUS) to deter potential enemies, train allies, and defend against aggression if needed. The institutional Army supports the operational Army by providing the training, education, and logistics necessary "to raise, train, equip, deploy, and ensure the readiness of all Army forces." Army organizations whose primary mission is to generate and sustain the Operating Forces, such as the Army Materiel Command (AMC), for example, are part of what is known as the Generating Force.

Army Command Structure

There are three types of commands: Army Commands, Army Service Components Commands (ASCCs), and Direct Reporting Units (DRUs).

Proposed Army Command Structure Changes: 2025 Army Transformation Initiative (ATI)

In May 2025, Army leadership announced the Army Transformation Initiative (ATI), with one of its initiatives to optimize force structure. Included in ATI's plans is a merger of Army Futures Command (AFC) and Training and Doctrine Command (TRADOC) into a single command under a single headquarters. Also under ATI, Forces Command (FORSCOM) is to transform into Western Hemisphere Command through the consolidation of Army North and Army South.

New Command Activations

As a result of ATI, the Army activated two new commands.

U.S. Army Transformation and Training Command

On October 1, 2025, the U.S. Army Transformation and Training Command (T2COM) was established as an Army command under the jurisdiction of Headquarters, Department of the Army by consolidating TRADOC and AFC.

U.S. Army Western Hemisphere Command

On December 5, 2025, the Army activated the U.S. Army Western Hemisphere Command (USAWHC) merging FORSCOM, U.S. Army North, and U.S. Army South into a single four-star headquarters. By February 2026, USAWHC is planned to reach initial operational capability (IOC) and full operational capability (FOC) by summer 2026. On December 2, 2025, the Army announced the following unit reassignments, effective December 5, 2025:

I Corps was reassigned to United States Army Pacific (USARPAC);

III Corps was reassigned to United States Army Europe-Africa (USAREUR-AF);

XVIII Airborne Corps, First Army, 20th Chemical, Biological, Radiological, Nuclear, and Explosives Command, and Air Traffic Services Command were reassigned to USAWHC; and

4th Infantry Division was reassigned to the I Corps.

Army Commands

Army commands perform many Title 10 functions across multiple disciplines. At present, the three Army Commands include Army Forces Command (FORSCOM), Transformation and Training Command (T2COM), and Army Material Command (AMC).

Army Service Component Commands (ASCCs)

ASCCs are operational organizations aligned with combatant commands. The ASCC commander is responsible for advising the combatant commander on the allocation and employment of Army forces within the combatant command. There are nine ASCCs, with five ASCCs aligned with geographic combatant commands and the remaining four ASCCs aligned with functional combatant commands. According to the Army, as a result of ATI, these ASCCs are to include

U.S. Army Central (USARCENT);

U.S. Army Europe and Africa (USAREUR–AF);

U.S. Army North (USARNORTH) (reassigned to USAWHC);

U.S. Army Pacific (USARPAC);

U.S. Army South (USARSOUTH) (reassigned to USAWHC);

U.S. Army Cyber Command (USARCYBER);

U.S. Army Transportation Command (ARTRANS);

U.S. Army Space and Missile Defense Command (USASMDC); and

U.S. Army Special Operations Command (USASOC).

Direct Reporting Units (DRUs)

DRUs have institutional or operational functions and provide broad, general support to the Army. According to the Army, as a result of ATI, these 15 DRUs are to include

U.S. Army Acquisition Support Center (USAASC);

U.S. Army Audit Agency (USAAA);

Arlington National Cemetery (ANC);

Civilian Human Resources Agency (CHRA);

U.S. Army Corps of Engineers (USACE);

U.S. Army Corrections Command (ACC);

U.S. Army Criminal Investigation Division (USACID);

U.S. Army Human Resources Command (HRC);

U.S. Army Intelligence and Security Command (INSCOM);

U.S. Army Joint Counter–Small Unmanned Aircraft Systems Office (JCO);

U.S. Army Medical Command (MEDCOM);

U.S. Military Academy (USMA);

U.S. Military District of Washington (MDW);

Military Postal Service Agency (MPSA); and

U.S. Army Test and Evaluation Command (ATEC).

Related CRS Products

CRS Report R48606, 2025 Army Transformation Initiative (ATI) Force Structure and Organizational Proposals: Background and Issues for Congress, by Andrew Feickert.

CRS In Focus IF10540, Defense Primer: Reserve Forces, by Kristy N. Kamarck and Carly A. Miller.