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This is part of the CSIS series U.S. Military Forces in FY2021. The U.S. Army plans slow expansion through FY 2025, but a constrained budget environment will force it to choose between maintaining the units it has and building new kinds of structures. With modernization, the Army has increased production of proven systems and shifted billions into development of high-priority programs to prepare the Army for great power conflict.

 Key Takeaways

  • After a dip in personnel strength in FY 2019, both regular and reserve components have recovered. FY 2021 targets include: regular Army, 485,900; Guard, 336,500; and Army Reserve, 189,800.

  • The regular Army and Army Guard project small increases through FY 2025; the Army Reserve will stay essentially level. This represents a substantial reduction to earlier growth plans, but probably the most expansion that can be done in the current budget and security environment.

  • New air and missile defense units are entering the force. Security Force Advisory Brigades continue despite their focus on stability operations. Other new kinds of units, such as the widely discussed multidomain brigades, remain mostly conceptual.

  • The active-reserve mix has stabilized at 52 percent Guard/Reserve, 48 percent active. There is now less tension between regular Army and its reserve components as a result of closer consultations, higher overall budgets, and shared recruitment challenges.

  • Army modernization, which forms the basis for future forces, is a mix of good and bad news: the good news is that the Army continues production of proven systems and has a well-modernized force as a result. More good news is a few new systems are coming out of the research, development, testing, and evaluation (RDT&E) “primordial soup.” The bad news is that the Army is still several years away from having a new generation of systems in production to take it into the 2020s and beyond and set it up for potential combat against great power adversaries.

  • In an environment of constrained resources, the Army will need to cut existing Brigade Combat Teams (BCTs) if it wants to build new units and procure new systems. So far it has been unwilling to do this.

Force Structure in FY 2021

Regular Army end strength recovered after a dip caused by recruiting and retention difficulties in FY 2019. In that year, the Army aimed for 487,500 but only attained 478,000. It moderated the goal for FY 2020 to 480,000 but was actually able to achieve 485,000. It proposes a small increase of 900 in FY 2021.

The pandemic has affected Army end strength. On the one hand, downturns make recruiting easier. On the other hand, recruiters must do most of their work online and thus have less personal contact. Also, pandemic related precautions such as social distancing limit the throughput in the training establishment. On balance, the effect seems to help end strength since the Army overachieved in FY 2020.

Civilian personnel levels dropped in FY 2020 but will return to their former level.

End strength for the Army reserve components showed a dip in FY 2019 similar to that seen in the regular forces but not the subsequent recovery. They have stayed at the lower end strength level but seem able to hold that.

The Army had fought hard against plans in the Obama administration to drop to 980,000 soldiers, regular and reserve, or lower. FY 2019 plans called for expansion to 1,040,000 by FY 2023, and Army officials had talked about even higher levels. However, such talk has nearly disappeared as the Army has struggled to maintain its current strength.

There are no major force structure changes in FY 2021. The regular Army maintains 31 Brigade Combat Teams (BCTs), and 11 Combat Aviation Brigades (CABs), with no net change from FY 2020 to FY 2021. The Army National Guard will maintain its current force of 27 BCTs and 8 Combat Aviation Brigades (CABs). The Army Reserve, which consists mostly of support units (“enablers”), retains two Theater Aviation Brigades (TABS).

There is a major difference in the BCT balance between the components. The National Guard is mostly infantry (74 percent). This reduces the need for vehicle maintenance, which is difficult with part-time personnel. The regular Army is more equipment intensive, with 58 percent of BCTs being medium or heavy.

As Table 3 shows, the total Army has also been getting heavier, which is unsurprising since it has reoriented itself from a focus on counterinsurgency, which needs infantry, to a focus on great power conflict, which needs firepower.

The Army has finished establishing the Security Force Advisory Brigades (SFABs), five in the regular force and one in the National Guard. SFABs train, advise, assist, enable, and accompany operations with allied and partner nations, thus reducing the burden on BCTs, which would otherwise have to deploy in pieces for this mission. The Army argues that SFABs support the National Defense Strategy (NDS) by enabling allies and partners, which is one of the NDS’s three major tenets. However, they have principally focused on irregular warfare and stability operations, to which the NDS gives a lower priority. Continuing all six SFABs indicates that the Army is maintaining some balance in its capabilities.

SFABs could also provide the basis for future BCTs if the Army needed to expand.

The Future Size of the Army

As shown in Chart 3, improved recruiting and retention have allowed the Army to get back on a growth slope that is higher than FY 2020, though not as high as what had been projected in FY 2019 and earlier. If the planned growth in the active and reserve components occurs, the Army will get back to its pre-9/11 level. In the long term, the regular Army hopes to get to 495,000.

Three opposing dynamics pull the future size and shape of the Army. One is the guidance in the NDS to focus on great power conflicts with Russia and China. That implies a force equipped with advanced, and likely very expensive, technologies paid for by cuts to structure, if necessary. Another is the day-to-day demand for forces to deploy to Afghanistan, Europe, and elsewhere. That implies a larger force that may not need the most advanced technologies. Finally, difficulties in recruiting and retention, as described earlier, may drive force size regardless of strategy.

The Army continues to note its global engagement: “187,000 soldiers deployed worldwide in 140 countries on six continents.”1 However, neither the Army posture statement nor any budget documents complain about stress. This likely occured because demands in the Middle East have declined substantially from their peak in the 2000s. That was the situation in February 2020. In October, the Army announced a reduction in rotations to combat training centers and in “heel-to-toe deployment rotations” because of “unsustainable operational tempo.”2 What caused this change in attitude toward stress is unclear. Also unclear is the effect it will have on readiness.

As Chart 4 shows, the Army Reserve had planned to increase to 200,000 and the Army National Guard to 343,000. Instead, both now aim for only small increases to their 2020 end strength.

Rather than increase size, the reserve components have opted to increase readiness. For example, the number of National Guard rotations to Combat Training Centers has continued at four. Nevertheless, both reserve components will suffer from understrength units, as force structure has not declined with the end strength plans.

Readiness is important because the reserve components need to sustain their status as an operational reserve. On average, about 25,000 Army Reserve and Guard personnel are mobilized at any time, mainly supporting operations in Iraq and Afghanistan.3 With high force demands on the Army continuing, this level of mobilization will likely persist indefinitely.

Balance of Regular and Guard/Reserve Forces

Bottom line up front: the Army as a whole seems to have reached equilibrium at 48 percent regular, 52 percent reserve components, a level attained in FY 2015 and projected to continue through at least FY 2025. Although the active/reserve mix has frequently been a source of tension in the Army, those tensions have eased in recent years as a result of closer consultation arising from a 2016 commission, higher budgets that benefit both components, and the difficulty that both components have in recruiting and retaining additional soldiers.

Nevertheless, given the different cultures, missions, and histories of the two components, the active-reserve mix is a tension that must be managed, not a problem that can be solved.

Tensions between regulars and reservists have existed since the beginning of the United States. This tension is particularly an issue for the Army because it has, by far, the largest reserve component, both in relative and absolute terms. For example, 52 percent of the total Army is in the reserve components, but only 35 percent of the total Air Force, 18 percent of the total Marine Corps, and 15 percent of the total Navy are in reserve components. As Chart 5 shows, Army reserve components (green) are nearly twice the size of all the other reserve components put together (in FY 2021, 525,000 versus 275,000).

As Chart 6 shows, the active/reserve balance has shifted over time. Establishment of the Total Force Policy in 1970, which called for increased reliance on the reserves, the initiation of the Volunteer Force in 1973, which raised the cost of military personnel, and the end of the draft in 1973, which cut off an easy supply of active-duty personnel, caused the ratio to move away from an active-heavy force to parity between the components.

With the end of the Cold War, the ratio changed to a reserve-heavy force as the regular force decreased more rapidly than the reserves.

The ratio reached parity again with expansion of the regular force during the wars in Iraq and Afghanistan but has returned to what appears to be a strategically stable level: 48 percent regular, 52 percent Guard/Reserve. Instead of large growth in either the regular or Guard/Reserve force, the Army, and the Department of Defense in general, has turned to contractors, as discussed in a later section.

Tensions between the components peak during drawdowns, when constrained resources force difficult trade-offs. Thus, there was a crisis in the late-1990s during the post-Cold War drawdown and another in 2014 during the post-Iraq/Afghanistan drawdown. Key to easing recent tensions was the 2016 National Commission on the Future of the Army. The commission looked broadly at all the components and the total Army’s needs and published a set of recommendations that all components could accept.4 The recent budget increases have helped implement the commission’s recommendations and eased tensions generally, as the Army does not need to make trade-offs between the components.

However, a budget downturn might bring these tensions to the surface again. Further, a national defense strategy that requires rapid reaction―as the NDS comes close to doing―would also increase tension by moving capabilities from the reserve components to the active components.

The reserves, particularly the National Guard, are politically powerful because of their connection to home-state political establishments. If they feel slighted, they can―and often do―bypass the Army hierarchy and take their concerns directly to Congress.

The Future Structure of the Army: New Kinds of Units

Consistent with the NDS, Army statements focus on great power conflict and moving beyond the regional conflicts of the last 20 years. However, these Army statements place relatively more emphasis on Russia, identifying it as the principal near-term threat, with China as a longer-term threat.5 That is not surprising since the Western Pacific theater consists mainly of ocean and long distances. The European theater would have greatest need for ground forces with advanced weapons. The Army is not ignoring the Pacific. It is working to develop capabilities that would be applicable there, such as long-range anti-ship missiles. Further, a conflict in Korea would require large U.S. ground forces.

This high-end conflict implies a force, perhaps a smaller force, that has advanced systems for ground combat, fires, and aviation. It also implies a force that has different kinds of capabilities such as cyber, electronic warfare, anti-ship/sea control fires, cruise and ballistic missile defense, and very long-range precision fires. Creating this force in an environment of constrained end strength will require cutting some existing capabilities, such as BCTs, a step the Army has not yet been willing to take.

A few new kinds of units are taking shape.

Cyber: Cyber expansion seems to be complete since it has mostly disappeared from Army statements. The Army created cyber units quickly to get this new capability into the field and experiment with it, though there was criticism that the Army did not have enough personnel with the right skills. Although cyber receives a lot of attention, the Army component numbers only several hundred personnel.6 Longer-term, the Army intends to build integrated intelligence/cyber-electronic warfare units as part of the multidomain forces.

Air and missile-defense: These units will be the first new kinds of combat units fielded. The Indirect Fire Protection Capability, designed to defend fixed points against cruise missiles and UAVs, will be fielded in FY 2022. The Maneuver-Short Range Air Defense is being procured now and will be fielded in FY 2023.

Multidomain units: These remain conceptual, although the Army has published concepts and conducted experiments using artillery brigades as the base unit. Multidomain units would integrate space, cyber, air, ground, and maritime “to execute simultaneous and sequential operations using surprise and the rapid and continuous integration of capabilities across all domains to present multiple dilemmas to an adversary.”7 The Army’s overall concept is called AimPoint, and the current thinking is that the major changes will occur at higher echelons, division and above.8

Pre-positioned equipment: The Army is building an additional set in Europe, thus increasing its rapid reinforcement capability. Extra funding from the European Deterrence Initiative has been key in building/rebuilding pre-positioned unit sets. The Army is examining additional pre-positioning in the Pacific.9

The Future Structure of the Army: New Capabilities

Looked at broadly, Army modernization is a “good news, good news, bad news” story: the good news is that the Army continues production of proven systems and has a well-modernized force as a result. More good news is that a few new systems are coming out of the RDT&E “primordial soup.” The bad news is that the Army is still several years away from having a new generation of systems in production to take it into the 2020s and beyond and set it up for potential combat against great power adversaries.

Modernizing the Current Force

In the near term, the Army is sensibly plugging its most serious capability gaps by upgrading the major systems it has and producing these systems at relatively high rates. As CSIS acquisition experts Andrew Hunter and Rhys McCormick point out, focusing on capabilities through upgrades rather than developing major new systems avoids the technical, budgetary, and political risk of relying on a few costly, high-profile programs.10

Thus, the Army FY 2021 budget funds the latest versions of existing systems. These programs run smoothly, produce equipment at known costs and on predictable schedules, and avoid acquisition scandals that in the past embarrassed the Army in front of Congress and the public.

Two relatively new programs are also in production: the Joint Light Tactical Vehicle, an armored light truck and replacement for the up-armored HMMWVs, and the Armored Multipurpose Vehicle, a replacement for the M113 armored personnel carrier.

The effect of this approach, combined with the large wartime procurements and rebuilds/upgrades funded by Overseas Contingency Operations (OCO) reset during the 2000s, is that the Army’s force structure is filled with relatively new equipment. For example, the Apache fleet averages 8 years and the Chinook fleet 10 years.11 Gone are prewar concerns about aging equipment fleets.

Finally, the Army’s FY 2021 budget, like the other services, continues robust funding for munitions, for example, the Guided MLRS rocket, the Hellfire antitank missile, and Patriot missiles (MSE). This reflects preparation for the intense combat that conflict with a great power would entail.

Creating New Capabilities

A long-standing concern about Army modernization is that there are few new systems coming online to replace the existing generation. This was the result of a “triple whammy”: a missed procurement cycle due to program failures, a focus on near-term systems for wartime operations, and modernization funding reductions in the postwar drawdown.12

The Army has divided its development effort into six major priorities (sometimes known as “the big six”): Long Range Precision Fires (artillery), Next Generation Combat Vehicle (armor), Future Vertical Lift (aviation), Army Network, Air and Missile Defense, and Soldier Lethality (infantry). The Army has added two more capability areas―Assured Positioning, Navigation, and Timing and Synthetic Training Environment―so the modernization effort is now “6+2.”

Chart 7 shows funding for the modernization priorities. Most funding is still in R&D, with only air and missile defense and soldier lethality showing significant procurement. Changes from FY 2020 to FY 2021 are modest, except for increases in air and missile defense and soldier lethality to cover procurement.

The Army points to 31 systems in development (the RDT&E “primordial soup”), far more than it can afford to procure and field. The Army’s chief resource manager warned, “[a]s those 31 signature systems come to maturation and it’s time to put things through a production line, that’s where we’re going to be making some difficult choices.”13

Shown below are major initiatives in development. The list gives a sense of systems that might enter the force in the future.14

Mark Cancian (Colonel, USMCR, ret.) is a senior adviser with the International Security Program at the Center for Strategic and International Studies in Washington, D.C.

This report is made possible by general support to CSIS. No direct sponsorship contributed to this report.

This report is produced by the Center for Strategic and International Studies (CSIS), a private, tax-exempt institution focusing on international public policy issues. Its research is nonpartisan and nonproprietary. CSIS does not take specific policy positions. Accordingly, all views, positions, and conclusions expressed in this publication should be understood to be solely those of the author(s).

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