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Theater Armies

Complex Yet Indispensable to Multidomain Operations

 

Lt. Col. Matthew A. McGrew, U.S. Army, Retired
Maj. Brandon J. Schwartz, U.S. Army

 

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Army organization above corps, with its links to the joint and combined environment, is less easily described and understood than the structure at corps and below.

—Lt. Gen. John Yeosock, Commanding General, Third U.S. Army

 

Theater armies are the most obscure Army echelon. Nevertheless, their complex mission is indispensable to Army support to joint force campaigns through multidomain operations (MDO). Theater armies (TA) provide an extensive breadth of capabilities such as theater-level sustainment, intelligence, fires, information advantage activities, protection, signal, aviation, medical, and civil affairs formations and staffs. TAs also provide unique access to the joint- and national-level enterprise. As the Army integrates MDO, most leaders tend to focus on the corps and division as the decisive echelons for large-scale combat operations in the land domain. However, to be decisive, the corps and division must have areas of operation properly managed by a TA, which enables their focus on achieving their objectives in close combat. In other words, the TA is the most significant enabler of MDO.

Theater Army History

The Army designed TAs to fulfill theater-level requirements identified during numerous conflicts. Today’s TA is recognizable back to World War I.¹ By the end of the war, the American Expeditionary Forces in France consisted of over two million soldiers organized into three armies, seven corps, forty-one divisions, the Army Air Corps, and the supporting Services of Supply.²

The Army shrank in the interwar period but quickly expanded again during World War II. By 1945, the Army had over 5.8 million uniformed personnel with 1.1 million organized into eighty-nine divisions.³ The remaining manpower comprised corps and above formations to support and enable the divisions. In 1945, the Army consisted of six theater headquarters, three Army groups, and nine field armies.⁴ Today, it contains no Army groups, one field army, and five TAs.⁵ Decreasing the quantity of formations above the corps echelon concentrated tasks almost exclusively to the TA, increasing the complexity of their operations. It also increased the strategic significance of TAs by making them the sole formation responsible for theater-level activities, which are the foundation of all Army operations.

Theater Army Roles and Responsibilities

TAs are both an echelon and a formation. They operate at the intersection of the theater strategic and operational levels of warfare, which is its primary distinguishing characteristic compared to corps and divisions. TAs translate the joint force commander’s (JFC) objectives into Army-specific campaigns and operations. This echelon links strategic objectives to tactical actions performed at the corps level and below. As the Army’s highest echelon, the TA represents the connection between the Army Secretariat and Staff and the combatant commanders (CCDR). As a formation, the theater army is comprised of a command group, headquarters staff, and assigned subordinate formations. The TA plans and assesses operations in support of the CCDR while overseeing subordinate preparation and execution of those operations.

By Army doctrine, the TA performs a combination of four different roles. Its primary role is as the Army Service component command (ASCC) to CCDRs with geographic areas of responsibility (AOR). TAs can also operate in one of three joint roles, which are typically performed during operations of limited scope, scale, and duration. These roles include theater joint force land component command, joint force land component commander, and joint task force headquarters. However, their capability to serve in joint roles is limited because of ASCC requirements.

 

 

TA commanders possess an extremely broad set of responsibilities derived from Title 10, executive agency, and direct operational support to CCDRs. As the ASCC, TAs are responsible in their combatant command’s (CCMD) AOR for executing the secretary of the Army’s congressionally mandated Title 10 requirements.⁶ TAs routinely do this by executing the administration and support of all Army forces deployed to or transiting the AOR; providing administrative control (ADCON) and Army support to forces deployed in a joint operations area inside the AOR; coordinating, supporting, and integrating all Army forces committed to the AOR in the CCMD campaign plan; and exercising operational control of all Army forces within the AOR not assigned to a joint commander.⁷

TAs also fulfill the secretary of the Army’s Department of Defense executive agent (EA) responsibilities within the theater. EA is the delegation of authority by the secretary of defense to a subordinate to act on their behalf to fulfill legal requirements, accomplish objectives, or minimize redundancy. Some of the most significant Army EA functions include theater detainee operations, theater chemical and biological defense, and counter-small unmanned aircraft systems.⁸

Finally, TAs must support the CCDR’s daily operational requirements. The CCDR’s authority to direct requirements and the Department of the Army’s responsibility to support are derived from Title 10.⁹ The specific requirements for support vary by AOR and include a broad set of responsibilities. The daily operational requirements generally include Army support to other Services (ASOS), providing Army forces for theater security cooperation, assessing and developing infrastructure, developing contingency plans for land operations, and providing intelligence-related indications and warnings of changes in an operational environment (OE).¹⁰

The Army further delineates the TA’s responsibilities through its description of the echelon’s seven functions, which must be performed daily.¹¹ TA functions include

• executing CCDR’s daily operational requirements;
• providing ADCON of Army forces;
• setting and maintaining the theater;
• setting and supporting operational areas;
• exercising command and control over Army forces in the theater;
• performing joint roles of limited scope, scale, and duration; and
• planning and coordinating for the consolidation of gains in support of joint operations.¹²

Consequently, the TA must maintain an AOR-wide focus, providing Army support to all Army and joint forces across the AOR, in accordance with the CCDR’s priorities of support. Army resourcing decisions to support TA requirements are often made on a case-by-case basis, balancing risks in a specific theater with other Army mission requirements.

TA roles and responsibilities require them to operate across the three Army strategic contexts. During competition, TAs gain relative advantages over adversaries by strengthening landpower networks, setting and maintaining the theater, and demonstrating readiness for armed conflict through the command and control (C2) of Army forces.¹³ During crisis, TAs conduct reception, staging, onward movement, and integration (RSOI) of land forces moving into theater and support the planning and employment of Army forces in flexible response and deterrence options.¹⁴ During armed conflict, TAs enable and support joint force land component commanders’ employment of land forces and play a key role in transition to postconflict competition.¹⁵

The TA is most effective when operating solely as an ASCC. The ability for a TA to maintain a persistent presence in its CCMD’s AOR is essential to the success of MDO. In the physical dimension of the OE, presence is indispensable for deterring adversaries and assuring allies and partners. TAs maintain presence forward through the deployment of command posts, the employment of assigned army forces in security cooperation activities, and development of strategic infrastructure. This presence also facilitates developing enduring relationships in the human dimension of the OE. The combination of physical presence and human relationships translates into an opportunity to gain and maintain information advantage over adversaries in an AOR, which protects U.S. freedom of action. While corps and divisions enable the TA’s security cooperation activities and perform operations during crisis and conflict, they are not designed to develop the enduring advantages in an AOR that a TA’s persistent presence does as the ASCC.

Theater Army Staff and Supporting Formations

As the Army’s highest echelon, TAs are designed with a more robust staff and C2 capability than lower echelons. Functionally, the TA staff conducts all the planning and assessing activities necessary for theater operations. They serve the CCDR by informing the CCMD’s staff on the capabilities of Army forces and shaping their proper employment. They also communicate the CCDR’s requirements to the Army staff and shape resourcing decisions within the context of the AOR.

 

 

Structurally, the headquarters staff supports the TA commander’s C2. The heart of the staff resides with the command group in the main command post. The main command post is not designed to deploy; rather, it is primarily responsible for Title 10, ADCON, ASOS, EA, planning, and coordination. These responsibilities are most effectively executed through dedicated, persistent focus in the AOR, which subordinate echelons are not designed to perform. TAs also have a contingency command post (CCP). The CCP is an operational headquarters capable of deploying its personnel and equipment by air to conduct operations of limited scope and scale during competition or crisis. The CCP commander can C2 two to five subordinate units up to brigade size but cannot exercise C2 for protracted military operations or combat operations unless appropriately augmented or reinforced. Ultimately, the CCP creates flexibility for land domain C2 with a staff who is already assigned and familiar with the theater.

The Army assigns TAs enabling capabilities and provides them access to an assortment of functional and multifunctional units. Specific formations vary depending on the requirements specific to the AOR. Standard theater-level enablers include a theater sustainment command, theater medical command, signal command (theater), civil affairs command, and military intelligence brigade–theater (see figure 1). As theater operations expand, additional theater-level forces may include an Army air and missile defense command; a security force assistance brigade; a chemical, biological, radiological, nuclear, and explosives command (CBRNE); engineers; military police; a battlefield coordination detachment; regional support groups; theater liaison detachments; and Army field support brigades.¹⁶

The subordination of these units to the TA is essential to MDO. Corps and subordinate echelons do not possess the staff capacity and span of control to effectively manage so many disparate organizations. Even if augmented, the corps and subordinate echelon commanders would then have to split focus on conducting operations and performing the previously described roles of the TA. TAs therefore conduct MDO, especially during conflict, by providing unity of effort to the administrative and support aspect of Army operations. In addition, they may fulfill the role of land component command, thereby maximizing the focus of tactical-level echelons on combat operations. Finally, TAs operate with many theater-level forces on a routine basis, maximizing their ability to quickly integrate into large-scale combat operations in an AOR.

Evolving Warfare

The Army is constantly transforming to adapt to the rapid evolution of warfare. Warfare, defined as the conduct and characteristics of war, evolved in the last century alongside the industrial revolution, the information revolution, and the present data revolution.¹⁷ The rapid technological evolution and corresponding military adaptation displayed in recent conflicts is changing warfare, forcing joint and Army forces to reconsider how they are organized, how they need to fight, and requirements for that fight.

In particular, new technologies relating to intelligence, surveillance, and reconnaissance and fires challenge how armies operate in the land domain. In the air domain, the proliferation of drones with advanced sensors have made it more difficult to conceal personnel and equipment. When paired with advanced fires capable of accurately targeting and rapidly engaging, the sensor-to-shooter connection is highly lethal. As Gen. Kenneth McKenzie, former commander of U.S. Central Command, stated, the proliferation of small, cheap drones is the “most concerning tactical development” since the rise of the improvised explosive devices in Iraq and represents “a new component of warfare.”¹⁸ Drone usage globally such as the war in Ukraine demonstrate the increased lethality resulting from sensor-to-shooter linkages from drones.¹⁹ The proliferation and effectiveness of drones require land forces to adapt their tactics and capabilities, such as increasing tactical dispersion and focusing on air defense and electronic warfare capabilities.²⁰ The reality of drone proliferation in the OE is reflected at the TA level, where combatant commands are increasing demands on the Army for tactical and operational air and missile defense capabilities.

High above the drones in the space domain, the proliferation of adversary space-capabilities over the last twenty years has eroded a key U.S. advantage. Adversaries have demonstrated increased ability to effectively employ space-based assets to improve their targeting and coordination. This will force changes to how Army forces operate. The (re)discovery of electromagnetic warfare as a powerful tool of war to counter these threats and attack adversary forces also affects how Army forces conduct operations. Cyberattacks and information campaigns will pose significant challenges abroad on operations as well as in the United States as the homeland is no longer a sanctuary. Finally, advances in machine learning and computing power leveraging big data and improved programming will provide a competitive advantage to those military forces able to harness them to drive better processes and faster decision cycles.²¹ Consequently, TAs are experiencing increased demands for space operations and cyber electromagnetic activities planning and capabilities.

In recognition of these changes, the Army recently adopted MDO as its operational concept. “Multidomain operations are the combined arms employment of joint and Army capabilities to create and exploit relative advantages that achieve objectives, defeat enemy forces, and consolidate gains on behalf of joint force commanders.”²² “It is how Army forces contribute to and operate as part of the joint force.”²³ Successful MDO rest on four tenets: agility, convergence, endurance, and depth.²⁴ TAs enable combined arms formations to operate with the necessary endurance and depth to create and exploit relative advantages. The TAs’ ability to employ capabilities from multiple domains helps to preserve combat power while providing JFCs options that create flexibility. TA operations also enable agility by setting conditions for operational movement that is quicker than our adversaries.

The rest of the joint force is adopting new operational concepts as well. The Air Force’s new operational concept, Agile Combat Employment, shifted its operations from centralized locations to a network of smaller, dispersed locations to protect air forces, complicate adversary planning, and provide additional options for JFCs.²⁵ Both the Navy and the Marine Corps have adopted new concepts as well, Distributed Maritime Operations and Expeditionary Advanced Base Operations, respectively.²⁶ Like Agile Combat Employment, Distributed Maritime Operations and Expeditionary Advanced Base Operations focus on dispersing naval forces while controlling key maritime terrain to provide more options for JFCs. The focus on dispersion and mobility will stress the Army’s ability to provide timely support to joint forces. Until additional joint experiments and war games integrate these new concepts, the impact of the increased ASOS bill of requirements remains largely undefined.

Challenges for Theater Armies to Overcome

MDO and modern warfare are driving changes in the focus of TAs. In the current OE, the ability of joint forces to conduct operational maneuver depends on the ability to protect, sustain, and C2 expeditionary forces. TA adaptation to these challenges will largely determine the Army’s future operational success.

One overarching challenge impacting TA functions is the Army’s component (COMPO) structure and force mix. Most CCMD contingency plans require expanded Army operations to support the joint force. Theater assigned and allocated forces are typically insufficient to the increased demand and create a shortfall in capability for the TA. While the shortfall is partially filled by the Army’s COMPO 1 (active duty) response forces, most required capabilities are provided by COMPO 2 (National Guard) and 3 (Army Reserve) forces, which usually require extended timelines to be available for employment.²⁷ However, this is problematic because they are often immediately required. This challenge is not restricted to specific echelons or warfighting functions. TAs can mitigate the resulting risk through numerous controls, but it cannot be eliminated. Therefore, the force mix and component structure challenge is reflected in the following warfighting function related challenges, where appropriate.

When CCDRs establish a joint operational area (JOA), they increase the TA’s protection requirements. Protecting forces is more difficult today because of increasing battlefield transparency and adversaries who can target and attack forces across the depth of the AOR. Defending against adversary threats requires increased capability and capacity in the TA to employ air defense, CBRNE, area protection, and force health protection operations throughout the AOR. In particular, the proliferation of small, capable drones and loitering munitions will require increased short-range air defense capabilities for point defense of dispersed locations. Additionally, threat magazine capacity exceeds Army air and missile defense capacity, providing enemies the opportunity to overwhelm area defenses in a high-volume attack or to win the battle for local missile/interceptor superiority through attrition.

The establishment of a JOA also increases the demand for Army signal support for operations. While dispersion can aid protection, it also increases signal support requirements. For example, dispersed command posts down to the division level creates communication architecture bandwidth requirements that currently exceed tactical system capabilities. TAs must establish the theater communications architecture capable of meeting joint force requirements.²⁸ Most of the TA signal assets are in COMPO 2 and 3, further complicating supporting signal operations.

Signal concerns add to TA C2 challenges. Joint RSOI is usually an Army responsibility requiring multiple C2 nodes and intermediate headquarters. Most of those additional headquarters like regional support groups, maneuver enhancement brigades, and engineer brigades are in COMPO 2 and 3, complicating effective C2. When multinational forces join operations, the joint force will require a robust liaison capacity to conduct operations. The Army provides those forces in the form of theater liaison detachments, all of which are COMPO 2 and 3. Additionally, C2 becomes exponentially more difficult if the TA is tasked to perform one of its joint headquarters roles. For example, during Operation Inherent Resolve, Third Army experienced difficulties establishing unity of effort in the land domain when the headquarters assumed the role of Combined Joint Task Force–Operation Inherent Resolve.²⁹

Setting and maintaining a JOA also increases the requirements for Army sustainment. Supporting operational maneuver over expanded distances requires a flexible, responsive, and protected sustainment network and physical infrastructure capable of supporting joint and multinational operations. Additionally, TAs depend upon COMPO 2 and 3 sustainment units to meet increased sustainment demand during a crisis or conflict. The actions that Army and joint forces take to survive while conducting operations will also complicate sustainment efforts. The more the joint force disperses, the greater the sustainment and protection challenges.

The final complication for TAs is performing their functions in operational areas with noncontiguous borders, especially maritime environments. Joint support requirements will likely increase, as air and maritime are typically the key to the JFC’s operational approach.³⁰ However, Army requirements to support dispersed air and maritime forces are still under development and undergoing refinement, compounding already identified challenges in protection, sustainment, and C2. In general, theater sustainment will be more difficult simply due to the highly collaborative requirements of a maritime environment. Protection of extended and exposed lines of communication will be another TA problem. Finally, forward forces assigned or allocated to the TA create protection and C2 challenges. Protecting them during crisis and initial conflict is vital. Then, TA commanders may have to fight forward forces until other echelons arrive to establish subordinate C2 structures. All of this will be complicated by the adversary antiaccess/area denial (A2/AD) networks and the TA commander’s requirement to assist with its defeat, at least until a subordinate land component command is established.

Way Forward

The TA is evolving to meet these challenges. The Army is fielding new theater-level organizations that the TA will employ in various strategic contexts. These organizations include the multi-domain task force (MDTF), theater fires command, theater strike effects group, and theater information advantage detachment (see figure 2). These organizations provide new capabilities to the TA and JFCs while enhancing the land component command’s ability to contribute to large-scale combat operations in MDO. For example, the MDTF synchronizes long-range precision lethal and nonlethal effects and long-range precision fires to assist the joint force’s efforts to defeat enemy A2/AD networks to enable freedom of action. Even in competition, the MDTF can integrate joint, interagency, intergovernmental, and multinational capabilities and data to gain and maintain contact with adversary A2/AD networks.³¹

The additional demands of modern warfare also require evolution of the TA staff structure. The TA of 2030 increases personnel across the staff to increase capacity in current operations, future operations, intelligence, counterintelligence, fires/targeting, space, cyber, integrated air and missile defense, and sustainment. The priority TA staffs are projected to grow as much as 60 percent as part of Army 2030 (see figure 3). Staff expansion enables commanders to better integrate the new, complex organizations assigned and allocated to their headquarters. For example, the MDTF creates interdependencies across unified action partners. The staff must enhance its capacity to handle these new requirements, as the TA’s responsibilities have not decreased. Consequently, it is essential to maintain the projected growth for the TA to enable subordinate echelons during MDO.

Conclusion

TAs are essential to the success of the Army and the joint force in competition today and crisis or conflict tomorrow. No other echelon in the Army can perform the expansive roles and responsibilities of the TA without extensive augmentation. Even then, those echelons would not have the persistent presence in an AOR or the routine interaction with the CCDR to be as effective as today’s TA. Evolving the TA is critical to ensuring its readiness to perform its mission through MDO in an increasingly complex OE, supported by a growing number of theater-level enablers. The Army should also reconsider the COMPO mix and assignment of critical theater enablers to ensure flexibility and responsiveness. There may be an opportunity to better balance the Army at the TA echelon by ensuring key formations are COMPO 1 and Service Retained. All of this ensures that the TA enables subordinate echelons to deter or defeat adversaries and achieve national strategic objectives.

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Notes

• Epigraph. John J. Yeosock, “Army Operations in the Gulf Theater,” Military Review 71, no. 9 (September 1991): 3.

1. For an in-depth treatment of this history, refer to John Bonin, “Echelons above Reality: Armies, Army Groups, and Theater Armies/Army Service Component Commands (ASCCs),” in Essential to Success: Historical Case Studies in the Art of Command at Echelons above Brigade, ed. Kelvin Crow and Joe R. Bailey (Army University Press, 2017), 251–65.
2. Ibid., 254.
3. Ibid., 255.
4. Ibid., 264.
5. U.S. Army Europe and Africa supports both U.S. European Command and U.S. Africa Command.
6. 10 U.S.C. § 7013(b)(1)-(12) (2021). The functions of the Department of the Army include recruiting; organizing; supplying; quipping; training; servicing; mobilizing; demobilizing; administering; maintaining; and construction, outfitting, and repair of military equipment, buildings, structures, and utilities.
7. Army Techniques Publication (ATP) 3-93, Theater Army Operations (U.S. Government Publishing Office [GPO], 2021)
8. U.S. Department of Defense (DOD) Directive 5101.01, DoD Executive Agent (U.S. DOD, 2022). Executive agents can change over time. They are managed by DOD Directive 5101.01, and a list of the specific functions are maintained by the DOD Executive Agent website at https://dod-executiveagent.osd.mil/Agents/Search.aspx.
9. 10 U.S.C. § 164(c)(1)(A) (2023). The combatant commander is authorized to give “authoritative direction to subordinate commands and forces necessary to carry out missions assigned to the command, including authoritative direction over all aspects of military operations, joint training, and logistics.” 10 U.S.C. § 7013(c)(4) (2021). “The Secretary of the Army is also responsible to the Secretary of Defense for … fulfill[ing] the current and future operational requirements of the … combatant commands.”
10. Field Manual (FM) 3-94, Armies, Corps, and Division Operations (U.S. GPO, July 2021), B-3. Army support to other Services includes but is not limited to “missile defense, fire support, base defense, transportation, … general engineering, intra-theater medical evacuation, veterinary services, logistics management, communications, CBRN defense, … and explosive ordnance disposal.”
11. For additional information, see FM 3-94, Armies, Corps, and Division Operations; and ATP 3-93, Theater Army Operations (U.S. GPO, July 2021).
12. FM 3-0, Operations (U.S. GPO, 2022), 2-18.
13. Ibid., 3-1.
14. Ibid.
15. Ibid., chap. 4–6.
16. For a complete list, refer to ATP 3-93, Theater Army Operations, chap. 2.
17. “Evolving Technology Will Change Warfare,” Association of the United States Army, 17 May 2023, https://www.ausa.org/news/evolving-technology-will-change-warfare.
18. Kyle Rempfer, “Drones Are Biggest Tactical Concern since the Rise of IEDs in Iraq, CENTCOM Boss Says,” Military Times, 8 February 2021, https://www.militarytimes.com/news/your-army/2021/02/08/drones-are-biggest-tactical-concern-since-ieds-rose-in-iraq-four-star-says/.
19. John M. Cantin, “Ukrainian Unmanned Aerial System Tactics,” TRADOC G-2 Red Diamond, 8 October 2024, https://oe.tradoc.army.mil/2024/10/08/ukrainian-unmanned-aerial-system-tactics/.
20. Andrea Gilli, “Drone Warfare: An Evolution in Military Affairs,” NDC Policy Brief 17-22 (NATO Defense College [NDC], 21 October 2022), https://www.ndc.nato.int/news/news.php?icode=1754.
21. Avi Goldfarb and Jon Lindsay, “Prediction and Judgment: Why Artificial Intelligence Increases the Importance of Humans in War,” International Security 46, no. 3 (2022): 7–50, https://doi.org/10.1162/isec_a_00425.
22. FM 3-0, Operations, 1-2.
23. Ibid., 3-1.
24. Ibid., 3-2.
25. Air Force Doctrine Note 1-21, Agile Combat Employment (U.S. GPO, 23 August 2022).
26. Kenneth J. Braithwaite et al., Advantage at Sea: Prevailing with Integrated All-Domain Naval Power (U.S. Department of the Navy, December 2020).
27. For example, approximately 40 percent of division headquarters, 100 percent of maneuver enhancement and expeditionary combat aviation brigades, 60 percent of infantry brigade combat teams, 66 percent of medical brigades, and 70 percent of inland cargo transfer companies are in components 2 (National Guard) and 3 (Army Reserve).
28. ATP 3-93, Theater Army Operations, 5-1.
29. Center for Army Lessons Learned (CALL), ARCENT Transition to Combined Joint Task Force–Operation Inherent Resolve, Initial Impressions Report No. 16-10 (CALL, March 2016), https://api.army.mil/e2/c/downloads/2023/01/19/bf0949b8/16-10-arcent-transition-to-cjtf-oir-lessons-and-best-practices-mar-16-public.pdf.
30. FM 3-0, Operations, 7-9.
31. Andrew Feickert, “The Army’s Multi-Domain Task Force (MDTF),” In Focus 11797 (Congressional Research Service, 10 July 2024), https://crsreports.congress.gov/product/pdf/IF/IF11797.

 

 

 

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