Ukraine is Forming Three New Army Corps—Should it Bring Back Divisions Too?

How should Ukraine organize its forces? The most important fighting units in Ukraine’s massive ground war to roll back the Russian invasion are the armed forces’ dozens of brigades of infantry and armor, each of which counts between 1,000 to 4,000 personnel.

Ukraine Corps Strategy

Organizationally, the prominence of the brigade is in line with most 21st-century armies. But what’s unusual is that Ukraine’s brigades aren’t assigned any permanent headquarters in a higher organizational echelon—like divisions, corps, or field armies. Instead, they’re shuffled between Ukraine’s four regional commands, which then undertake to provide vital logistical and combat support. 

This wasn’t always the case. After the dissolution of the Soviet Union, Ukraine’s armed forces inherited 14 divisions as well as three Army Corps HQs (two formed from former Soviet 6th and 8th Tank Armies) which were disbanded in 2004, 2013, and 2015.

The retirement of these large formations, unlikely to maneuver together on the battlefield, probably seemed practical and forward-thinking at the time. And the regional model seemed to work during the first year of Russia’s large-scale invasion, as Ukraine harnessed its secure interior lines of communication to rapidly shuttle its best brigades from one end of the country to the other, slotting in to stamp out operational crises or mount local counter-offensives, then rotating out as they got ground down from combat.

But with Ukraine’s armed forces massively expanded for this big war, some Western and Ukrainian experts think Kyiv might be better served to reintroduce higher HQs to ensure frontline troops are properly supported.

Richard Hooker, former dean of the NATO Defense College, wrote last August that the regional commands: “… lack true battle staffs that can integrate airspace, deep fires, logistics, intelligence, and higher-level command and control.” 

It’s not that nobody is trying to do those things, but rather that’s happening in a more improvised and uncoordinated manner than is ideal, as the more embattled regional commands have to meet the demands of a very horizontally-broad organizational chart. That may work to the detriment of Ukrainian combat units lacking an enduring relationship and continual services from the same higher headquarters.

Hooker argued Ukraine should convert its four territorial commands into Corps, each divided into two or three divisions. He also suggested the formation of a fifth corps of offensive armor and mechanized divisions held in reserve for counter-offensive operations.

Ukraine’s Powerful New “Corps”

Some changes along these lines are now happening, as Ukraine has announced the formation of three new corps. According to The Economist, each will have six frontline combat brigades, some outfitted with newly received Western armored vehicles, that may be employed for its Spring counter-offensive. The six maneuver brigades will doubtlessly be complemented by supporting brigades or battalions of artillery, air defense, combat engineers, and so forth under the control of the Corps HQs.

A corps (also known as “field corps” or “army corps”) is a large military unit ordinarily composed of two or more divisions (each usually with around 15,000 personnel), supported by a Corps HQ and various specialized support units. 

There are of course other military uses of the words ‘corps’ to denote a specialized body of personnel (like the Marine Corps, or the ‘NCO corps’ etc.) but that’s not the usage of corps we’re talking about here.

Corps tend to be less standardized than divisions or brigades, but average 40,000 to 60,000 persons though sizes well above or below aren’t uncommon historically. Multiple corps can be grouped together into an even larger unit known as an army or “field army.”

In practice, Russian “armies” are more comparable to a Western corps in composition, though Russia’s military retains some army corps in their force structure that is smaller than the Western equivalent. They’re generally a specialized regional grouping of brigades or regiments equivalent to or slightly larger than a division. These notably include: 

• 22nd Army Corps (Crimea area, heavily engaged in initial Russian offensive)
• 11th Army Corps (defending the Baltic enclave of Kaliningrad)
• 68th Army Corps (defending Sakhalin and Kurile islands)
• 14th Army Corps (defending the Arctic Murmansk)
• 3rd Army Corps (formed 2022 from volunteers looking to fight in Ukraine, has had little battlefield success)

Those not deployed to Ukraine, incidentally, have been reduced to shadows of their former selves as personnel from their sub-units have been stripped away to fight in Ukraine. 

An additional advantage of Ukraine’s news corps, compared to regional commands, is that they can shift their areas of responsibility across regional boundaries. However, the new corps still appear to lack the echelon in between corps and brigade: the division, which typically has two-to-four maneuver brigades each and usually numbers 10,000 to 15,000 personnel.

Ukraine and the downsides of horizontal organization

A Ukrainian officer posting by the Twitter handle Tatarigami commented on social media: “We need a larger structure, such as divisions, especially for large offensives. Another benefit is that you get specific people responsible for logistics, communication and synchronization, rather than ambiguous roles and duties that we have right now on that level.”

It is likely that the sheer number of units brigades attached to each regional command limits how effective and attentive it can be. Back in the 1950s, the U.S. Army adopted ‘Pentomic’ divisions, which traded a force structure based on units of three for one organized around units of five. But this resulted in a degradation of quality because commanders simply couldn’t manage the larger number of sub-units as effectively.

Having so many subunits also results in a competition for resources that often favors “rock star” units over those with less glamorous reputations who may get caught in a vicious spiral of failure and heavy losses.

Glenn Grant, a British defense analyst and advisor to Ukraine’s military, wrote that he fears the current structure lends itself to this:  “There are simply too many organizations working separately from each other and even at times in opposition. This creates pockets of “first, second and third “divisions of quality where some units are equipped and trained properly, and others are not… This lack of a common concept encourages organizational arrogance where some parts of the military system are considered better or more important than others and are both treated and act so. This attitude risks sending soldiers and volunteers to their death early because the system has not valued them sufficiently to prepare them properly for the realities of battle.”

Adding a divisional HQ, then, would guarantee a higher-level staff dedicated to providing various services for a smaller number of brigades. That usually includes mid-to-high ranking officers dedicated individually to functional roles: personnel, intelligence, operations and training, and logistics—and often also civil affairs, signals/cyber, and medical. It’s like how corporate leadership often includes functionally tasked CTOs, COOs, and CFOs.

The division would also dispose of support assets reserved for their frontline brigades—typically a brigade/regiment of artillery, and full battalions of other types of support troops.

To be fair, siloing resources this way may make it harder to redistribute them when mass is required. And a downside to more robust support and HQ presence is that this shifts personnel away from frontline roles to support/admin/and logistics jobs, a balance known as teeth-to-tail. The Russian/Soviet tradition favors a high ratio of teeth, while Western militaries emphasize robust logistical tails. 

The teeth-first approach guarantees more bodies and vehicles on the frontline—though they’re also more likely to get ‘spent’ due to casualties and logistical exhaustion. The argument for investing in the tail is that by ensuring frontline troops are better supported, a smaller number can remain effective for longer and with lighter casualties.

Though the new organization may require more support personnel, Hooker argues there may be a larger pool of human resources that can handle many of the non-combat tasks, meaning the reduction to combat troops might not be on a strictly zero-sum basis. 

Grant, though not in favor of a larger ‘tail’, nonetheless argues the Ukrainian Army should induct more civilians to take on support and administration roles, ensuring military personnel are channeled toward functions only they can be trained to perform.

Not everyone agrees that re-introducing larger formations is vital, however. Konrad Muzyka, a Polish defense analyst wrote to me: “Kharkiv Offensive showed [Ukraine’s military] had a flexible approach. They created new tactical-operational commands, which ran 4-5 brigades in their respective Areas of Responsibility (AORs).” 

In other words, creating temporary equivalents of divisions or Corps to execute a highly successful maneuver operation. That might draw from the Soviet doctrine of the Operational Maneuver Group, a temporary grouping of powerful mobile forces created to penetrate deep into enemy lines.

Konrad also pointed out that on the frontline, Ukraine’s army fights side-by-side with other branches of the armed forces like Marines, Territorial Defense Forces, etc.—units that couldn’t ordinarily be inducted into a permanent division or corps-level formation of the Ukrainian Army.

Of course, it’s ultimately up to Ukrainians to decide how their armed forces are best organized. While it has benefitted greatly from western training and advising, there’s also a risk that foreign advisors try to push templates from their ostensibly more modern advanced military culture that may actually be ill-suited to the context and realities of their advisees. 

Ukraine’s armed forces have so far blended their Soviet-military tradition with an influx of Western methods and technologies. Time will tell whether that ongoing adaptation leads to the reintroduction of additional higher headquarter units like Kyiv’s new corps that standardize support services to frontline units, or sticks closer to the ad-hoc approach Ukraine’s military relied on in 2022.

Sébastien Roblin has written on the technical, historical, and political aspects of international security and conflict for publications including 19FortyFive, Popular Mechanics, The National Interest, MSNBC, CNN, Forbes.com, Inside Unmanned Systems, and War is Boring. He holds a Master’s degree from Georgetown University and served with the Peace Corps in China.  You can follow his articles on Twitter.