Ukraine’s Military Transitioning to Corps-Based Command Structure

Ukraine’s Military Transitioning to Corps-Based Command Structure

Executive Summary:

• Since early 2025, Ukraine’s Armed Forces (AFU) have launched a transition to a corps-based command structure, making corps the largest operational units in the AFU, rather than brigades, and replacing temporary wartime groupings.
• The reform aims to establish permanent corps-level commands, improving accountability, coordination, and operational efficiency across various fronts after years of organizational improvisation.
• Each corps, composed of five to seven brigades and 60,000–80,000 troops, reports to one of four regional commands. Overlapping brigade subordination remains a major challenge, hindering unified control and slowing progress toward fully independent corps operations.
• The reform would align Ukraine’s military structure with North Atlantic Treaty Organization (NATO) standards, introducing corps–division–brigade organization to enable joint planning and interoperability. Shortages of trained senior officers, logistics bottlenecks, and limited staff experience threaten effective reform implementation.
• Corps are evolving into recruitment and training hubs, conducting two-month preparation courses for new personnel and coordinating mobilization, boosting efficiency but straining resources, requiring sustained investment in infrastructure, equipment, and instructors to maintain long-term combat readiness.

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Introduction

Since the beginning of 2025, the Armed Forces of Ukraine (AFU) have launched a transition to a corps-based system of troop command and control. In 2022, brigades were the AFU’s largest operational units. The new structure would make corps, comprising several brigades, the AFU’s largest operational unit (Kyiv Independent, October 13). This reform had long been overdue, as the AFU has grown several times over since Russia launched its full-scale invasion of Ukraine in 2022 (Militarnyi, June 22; see EDM, June 27).

The corps reform is also designed to eliminate so-called “temporary structures,” such as operational-strategic and operational-tactical groupings, introduced during Russia’s 2014 invasion of Ukraine. Operational-strategic groupings were meant to manage sections of the front line by coordinating the activities of multiple operational-tactical groupings, acting as intermediate command structures. Since they were temporary in nature, these groupings did not assume complete responsibility for decision-making and lacked the full capabilities required for a given sector of the front. They also lacked a clear hierarchy and chain of command; if there were problems on a particular sector of the front, such as an enemy breakthrough, the responsibility lay not with the head of the operational-tactical grouping, but with the brigade commander (Army Inform, May 12).

This has now changed in some cases, as some individuals have been removed not from their ranks but from their command posts within the corps. The corps reforms aim to clarify the chain of command by making the corps the permanent, primary organizational unit within the armed forces. This occurred in the 20th Corps, which was directly engaged on the Novopavlivka axis. Responsibility for a given sector of the front is placed directly with the corps commander (Babel.ua, September 23).

The corps reform would pass full command of the corps to the Joint Forces Command, but this has not yet occurred. As a result, the AFU currently has several interim structures that command the corps and serve as a link between the Ukrainian General Staff and the corps.

Corps Structure

Since the corps reform began, the AFU has consolidated temporary structures into four regional commands: the South, East, and West groupings of forces, which are conducting the main battles, as well as the North grouping of forces. The corps are directly subordinated to these regional commands—approximately three corps per regional command.

One corps consists of five to seven brigades. This includes a separate artillery brigade, a heavy mechanized brigade, and several mechanized or motorized infantry brigades. The total number of troops per corps ranges from 60,000 to 80,000, depending on the formations assigned to it.

The main challenge facing the corps reform is ensuring that each corps has a distinct set of brigades under its command. At present, most brigades remain under the operational subordination of multiple corps, which means that very few corps have singular command of their own units.

The corps reform is meant to streamline the management of units in a specific sector of the front. Internal reassignments can then be made at the corps level. For example, a brigade that performs successfully can serve as a model, with its experience scaled and applied to other brigades that lag in training or command quality. As with any military organism, the combat power of a corps is judged by its weakest unit (see EDM, June 27).

Certain mobilization experiments connected with recruiting and mobilizing directly into corps units are also being conducted. At least several corps, whether in the National Guard or the AFU, are currently engaging in such practices. Newly mobilized personnel are offered training at the corps’ training grounds, a two-month preparation course, and subsequent assignment solely into the corps’ units (24tv.ua, October 10).

“West” Grouping of Forces

The West grouping of forces is responsible for the Volyn, Rivne, Zhytomyr, Kyiv, Chernihiv, and Sumy oblasts, as well as the city of Kyiv. It is commanded by Brigadier General Shvediuk and includes four army corps (the 12th, 14th, 15th, and 18th Army Corps).

The full composition of the West Grouping includes: OPBr (Presidential Brigade “Hetman Bohdan Khemelnystkyi’)*, 1st Separate Heavy Mechanized Brigade (OVMBr), 1st Separate Territorial Defense Brigade (OBrTrO), 5th Separate Assault Brigade (OShBr)*, 10th Separate Mountain Assault Brigade (OGShBr), 21st Mechanized Brigade (OMBr), 22nd OMBr, 27th Artillery Brigade (OABr), 42nd OMBr, 44th OABr, 47th OMBr, 47th OABr, 58th Motorized Infantry Brigade (OMPBr), 66th OMBr, 67th OMBr*, 72nd OMBr*, 92nd OShBr, 101st OBrTrO, 104th OBrTrO, 105th OBrTrO, 106th OBrTrO, 112th OBrTrO, 118th OBrTrO, 120th OBrTrO, 129th OVMBr, 143rd OMBr, 144th OMBr, 151st OMBr*, 156th OMBr, 157th OMBr*, and 158th OMBr.

*These brigades are likely to be reassigned from the 12th Army Corps to other corps.

The West brigades (excluding mechanized brigades within the 12th Army Corps) include:

• Eight mechanized brigades
• Eight territorial defense (TrO) brigades
• Three heavy mechanized brigades
• Four artillery brigades
• One assault brigade
• One mountain assault brigade
• One motorized infantry brigade
• One separate presidential brigade

There are a total of twenty-three infantry brigades and four fire-support brigades.

With its current set of forces, the West grouping’s primary task is the complete expulsion of the enemy beyond the state border in Sumy oblast.

“North” Grouping of Forces

The North grouping of forces is responsible for the Kharkiv oblast and parts of the Luhansk oblast. It is commanded by Major General Krasylnykov and consists of five corps (3rd, 10th, 16th, and 21st Army Corps and the 2nd Corps of the National Guard of Ukraine (NGU)).

The whole composition of the North grouping includes: 3rd OShBr, 3rd OVMBr, 3rd NGU Operational Brigade, 4th OVMBr, 4th NGU Operational Brigade, 12th OVMBr, 13th NGU Operational Brigade, 14th OMBr, 17th NGU Brigade, 18th NGU Brigade, 26th OABr, 41st OMBr, 43rd OMBr, 48th OABr, 52nd OABr, 53rd OMBr, 57th OMPBr, 60th OMBr, 63rd OMBr, 93rd OMBr, 113th OBrTrO, 115th OMBr, 116th OMBr, 125th OVMBr, 152nd OMBr, 154th OMBr, 155th OMBr, and 159th OMBr.

The North brigades include:

• Thirteen mechanized brigades
• Five national guard brigades
• Four artillery brigades (1 uncertain)
• Four heavy mechanized brigades
• One motorized infantry brigade
• One territorial defense brigade
• One assault brigade

There are a total of 25 infantry brigades and four fire-support brigades.

The main task of the North grouping of forces in autumn–winter 2025 is to prevent the occupation of Lyman. The defense of Kupiansk has also been prioritized and assigned to the 2nd NGU Corps and the 10th Army Corps.

“East” Grouping of Forces

The East grouping of forces is responsible for Donetsk oblast, as well as parts of the Luhansk and Zaporizhzhia oblasts. It is not yet known who commands the grouping, and it consists of six corps (11th, 19th, 9th, 20th Army Corps, 1st NGU Corps, and the 7th Rapid Reaction Corps of the Air Assault Forces)

The full composition of the East Grouping includes: 1st NGU Operational Brigade, 5th OVMBr, 12th NGU Special Purpose Brigade, 14th NGU Operational Brigade, 15th NGU Operational Brigade, 17th OVMBr, 20th NGU Operational Brigade, 23rd OMBr, 24th OMBr, 25th Airborne Brigade (OPDBr), 28th OMBr, 30th OMBr, 31st OMBr, 32nd OMBr, 33rd OMBr, 40th OABr, 44th OMBr, 45th OABr, 54th OMBr, 55th OABr, 56th OMPBr, 60th OABr, 68th Separate Jaeger Brigade, 77th Separate Airmobile Brigade, 79th Air Assault Brigade, 81st Separate Airmobile Brigade, 110th OBrTrO, 117th OVMBr, 127th OVMBr, 141st OMBr, 142nd OMBr, 147th OABr, and 153rd OMBr.

The East brigades include:

• Twelve mechanized brigades
• Five national guard brigades
• Five artillery brigades
• Four heavy mechanized brigades
• Two airmobile brigades
• One air assault brigade
• One airborne brigade
• One Jaeger brigade
• One motorized infantry brigade
• One territorial defense brigade

There is a total of 28 infantry brigades and five fire-support brigades.

Among the first “failures” of the grouping was Russia’s advance toward Dnipropetrovsk oblast, which led to the removal of Colonel Maksym Kituha from command of the 20th Army Corps (Kyiv Post, September 16).

The main task of the East grouping of forces is to prevent the occupation of Siversk, eliminate the threat of a “blockade” of Pokrovsk, conduct targeted counterattacks to halt enemy advances, prevent a breakthrough toward Kostiantynivka, and hold the Donetsk–Dnipropetrovsk border zone in the sector of the 20th Army Corps.

“South” Grouping of Forces

The South grouping of forces is responsible for the Odesa, Mykolaiv, Kherson oblasts, and most of Zaporizhzhia oblast. It is commanded by Major General Sydorenko and consists of two corps (17th Army Corps and 30th Marine Corps).

The full composition of the South grouping includes: 32nd OABr, 34th Coastal Defense Brigade (OBrBO), 35th Marine Brigade, 36th Marine Brigade, 37th Marine Brigade, 38th Marine Brigade, 39th OBrBO, 40th OBrBO, 54th OABr, 65th OMBr, 108th OBrTrO, 110th OMBr, 118th OMBr, 128th OVMBr, 128th OGShBr, 241st OBrTrO, and 406th OABr.

The South brigades include:

• Four marine brigades
• Three coastal defense brigades
• Three artillery brigades
• Three mechanized brigades
• Two territorial defense brigades
• One heavy mechanized brigade
• One mountain assault brigade

There are a total of 13 infantry brigades and three fire-support brigades.

One of its corps has already drawn the attention of the Ukrainian General Staff and General Oleksandr Syrskyi personally due to the loss of the settlement of Kamianske in Zaporizhzhia oblast, which led to the removal of Colonel Volodymyr Sylenko from command of the 17th Army Corps (Kyiv Post, September 16).

The main task of the South grouping of forces is to limit the Russian forces’ offensive potential in Zaporizhzhia oblast.

Reform Outlook

The corps reform is part of Ukraine’s long-term alignment with North Atlantic Treaty Organization (NATO) standards. Since 2016, the General Staff has discussed introducing a corps–division–brigade system, but the project has been repeatedly postponed. The expansion of the AFU after Russia’s full-scale invasion made a corps reform unavoidable. The corps system is designed to mirror allied models of field corps and army groups, enabling the AFU to communicate in the same “operational language” as NATO partners and prepare for joint operations.

While the introduction of corps increases accountability and unifies responsibility for sectors of the front, it has also exposed a chronic shortage of trained officers at the divisional and corps staff level. Many newly created headquarters lack the institutional memory and operational experience to coordinate five to seven brigades simultaneously. Logistics, communications, and staff training remain critical weak points, and the success of the corps reform depends on whether these gaps can quickly be closed under wartime conditions.

The reform is not limited to the land forces. Several corps of the NGU and Air Assault Forces have been integrated into the new system. This demonstrates an effort to create a joint command structure in which all types of forces—army, airborne, and national guard—operate within a single corps framework. Such integration, however, requires harmonizing doctrines, communications, and mobilization pipelines across branches, which remains a work in progress.

A less visible, but no less important, aspect of the corps reform is its effect on mobilization. Corps headquarters are increasingly used as centers for recruitment, training, and deployment, with two-month preparation courses for mobilized personnel conducted at corps training grounds. This approach centralizes responsibility for reserves but also places a heavy burden on the state, which must provide equipment, instructors, and infrastructure at a scale far beyond pre-war planning.

The sustainability of this system will be a decisive factor for Ukraine’s ability to maintain combat effectiveness over time.