Army Sustainable Readiness Model: Phases, Measurement, and ReARMM

The Army Sustainable Readiness Model was the United States Army’s force generation framework from fiscal year 2017 through fiscal year 2021. It replaced ARFORGEN, the deployment-cycle system built for Iraq and Afghanistan, and was itself replaced by the Regionally Aligned Readiness and Modernization Model (ReARMM) in October 2021. Instead of pushing units through fixed phases tied to a known deployment date, SRM sorted them into three readiness modules and aimed to keep a broader share of the force ready to fight at any given time.¹

Why the Army Moved Off ARFORGEN

ARFORGEN, adopted in 2006, ran active-duty units through three annual phases (Reset, Train and Ready, Deploy) on a repeating three-year cycle. Reserve and National Guard units followed a five-year version: four years of preparation and one year deployed.² The system assumed deployment schedules would stay predictable, which worked while the Army was feeding a steady rotation into two known theaters.

By 2014 that assumption had eroded. Troop levels in Iraq and Afghanistan had dropped, and Army leaders concluded the next major threats were more likely to come from Russia, China, North Korea, or Iran — adversaries that would not oblige a scheduled rotation calendar.² The Budget Control Act of 2011 also squeezed Army funding for three consecutive years, forcing constant trade-offs among readiness, personnel, and force structure.³ ARFORGEN’s rigid cycles left units either surging to peak readiness right before a deployment or sitting in reset, with no built-in way to keep a wider pool of the force ready for a crisis that could break anywhere.

How the Sustainable Readiness Model Worked

The Army began implementing SRM in fiscal year 2017 with a stated goal: get two-thirds of Regular Army and Army National Guard brigade combat teams to a combat-ready status by 2023.¹ Rather than progressing units through fixed phases pegged to a deployment date, SRM described what a unit was doing at any given moment using three modules:

Mission Module. Units assigned to an ordered mission, fully resourced, validated, and immediately ready for decisive action, meaning they could conduct offensive, defensive, and stability operations.
Ready Module. Units maintaining baseline proficiency in decisive action tasks and available to deploy if a contingency arose.
Prepare Module. Units rebuilding readiness after a mission or during periods without an assigned deployment.²

The critical break from ARFORGEN was that active-duty units no longer moved through a fixed progression. A brigade in the Ready Module did not automatically slide into the Mission Module after a set number of months; the Army could pull from a wider pool of ready forces as global demands shifted. Reserve Component units, however, stayed on their familiar five-year cycle (four years of preparation and one year available) under both ARFORGEN and SRM.¹

General Robert B. “Abe” Abrams, then the commanding general of U.S. Army Forces Command, defined the model at an Association of the United States Army forum in July 2016 as “being ready all the time,” not just in the weeks before a deployment. A unit that deployed for a rotational mission was expected to maintain its combat standards while forward, perform routine maintenance on return, and be ready to go again within weeks. Abrams argued the old approach, in which readiness peaked at deployment and cratered during reset, was no longer survivable for an Army shrinking toward a total end strength of 980,000 soldiers across all three components while combatant commanders were demanding more rotational forces in Korea, the Middle East, the Pacific, Africa, and, starting in 2017, Eastern Europe.⁴

Under SRM, U.S. Army Forces Command remained responsible for training and maintaining over 750,000 active and reserve soldiers to fill the demands of geographic combatant commanders worldwide. Units were expected to be “surge-ready but rotationally focused,” capable of responding to a no-notice crisis while also meeting scheduled missions such as combat deployments, theater security cooperation, and global response requirements.⁵

How Readiness Was Measured

The 66-percent readiness target tied to the Army’s existing reporting system. Under Army Regulation 220-1, every battalion submits a Unit Status Report through the Department of Defense Readiness Reporting System-Army. The report scores four areas, each rated from 1 (highest) to 4 (lowest):⁶

P-level (Personnel). Soldiers on hand compared to required strength.
S-level (Equipment On-Hand). Quantity of equipment held against what the unit’s organizational table authorizes.
R-level (Equipment Readiness). Serviceability of that equipment, driven by operational readiness rates of critical “pacing items” such as tanks and helicopters.
T-level (Training Proficiency). The unit’s assessed ability to execute its mission-essential tasks.

The system had known distortions. Units sometimes delayed reporting broken vehicles until a reporting window closed, or cannibalized parts from non-reporting vehicles to keep pacing items technically operational, producing numbers that looked better on paper than in the motor pool.⁶ Whether the 66-percent aggregate target was actually met by 2023 is not conclusively documented in available records. One analysis from the operational side noted that deployed forces’ proficiency “tends to decrease with each passing month” because of outdated qualifications and insufficient collective training resources, suggesting the target remained aspirational for at least some formations.⁷

Abrams also flagged a persistent gap in deployment-to-dwell ratio at AUSA’s 2017 annual meeting. The Army’s goal was two years at home for every one year deployed, but the service had not achieved that ratio since 2004, hovering instead near one-and-a-third to one.⁸

Where SRM Fits in the Army’s Readiness Models

SRM was the third in a line of Army readiness frameworks stretching back to the Cold War, and it was not the last:

Tiered Readiness Model (1980s–2006). Units were manned, equipped, and trained at different levels based on their tier, focused on fighting potential overseas adversaries. Reserve Component forces served primarily as a strategic reserve, called up only in crises exceeding the Regular Army’s capacity.⁹
ARFORGEN (2006–2016). Built for rotational war, with three-year active-duty cycles and five-year reserve cycles driving predictable deployments to Iraq and Afghanistan.
Sustainable Readiness Model (FY2017–2021). Eliminated fixed cycles for the Regular Army in favor of continuous readiness across the Mission, Ready, and Prepare modules.
ReARMM (October 2021 forward). Reintroduced structured phases, adding regional alignment.¹

The Congressional Research Service flagged the frequency of these transitions as a potential source of organizational stress, questioning whether constant model changes help or hinder the force.⁹

What Replaced SRM

The Army announced ReARMM in October 2020 and adopted it in October 2021, with full operational capability planned for January 2023.¹ Where SRM had deliberately avoided fixed phases for active units, ReARMM brought back structured eight-month rotations through modernization, training, and mission-eligibility windows. The reasoning: without predictable schedules, it was nearly impossible to synchronize the fielding of new equipment with a unit’s training calendar.¹⁰

ReARMM also layered in regional alignment, assigning units to specific geographic theaters to develop expertise in local terrain, culture, and partner militaries, and to build habitual relationships with allies rather than showing up cold for a rotation.¹ The goal was to provide at least three units of the same size, type, and modernization level aligned against each combatant command’s requirements.

The January 2023 full-capability deadline slipped. Army officials told the Government Accountability Office that operational support to Ukraine following Russia’s February 2022 invasion, which required rapid deployment of elements from the 82nd Airborne Division, the 1st Infantry Division, and the 3rd Infantry Division, contributed to the delay. The Army finalized revised implementation orders in March 2024 but had not completed the formal regulation or pamphlet as of that report.¹¹

As of 2026, the Army is again transitioning, this time from ReARMM to a model called the Continuous Transformation Readiness Model, or CTRM. The Army planned to issue updated force generation guidance through a CTRM execute order in March 2026 while working to codify process changes into its force generation regulation, AR 525-29, which has not yet been published in its revised form.¹² CTRM’s full structural details have not been made public. Whether it marks a genuine departure from ReARMM or a refinement remains to be seen as the Army finalizes its updated regulation.

1
Congressional Research Service. Army Readiness: Regionally Aligned Readiness and Modernization Model
2
Every CRS Report. Army Force Generation and the Sustainable Readiness Model
3
U.S. Army Center of Military History. Department of the Army Historical Summary, Fiscal Year 2016
4
AUSA. Army Sustainable Readiness Model Means Being Ready All the Time
5
U.S. Army. Building and Sustaining Readiness Across Forces Command Formations
6
Army University Press. Unit Status Report
7
Army University Press. Readiness and Interoperability in Operation Atlantic Resolve
8
Fayetteville Observer. Abrams at AUSA: Army Must Be Ready Now
9
Every CRS Report. Army Readiness: Regionally Aligned Readiness and Modernization Model
10
U.S. Army. Operationalizing ReARMM: A Sustainment Perspective
11
GAO. Army Modernization: Actions Needed to Support Fielding New Equipment
12
GAO. Army Modernization: Actions Needed to Support Fielding New Equipment