In early February, I published a detailed forecast estimating the number of troops the Russians would have to deploy to successfully occupy part of Ukraine. In my notional scenario, I assumed the Russians would only advance as far as Kharkiv and the lower Dnieper river. Using military troop-to-task analysis, I estimated Russia would have to deploy 83,000 troops to secure that part of Ukraine and keep another 83,000 in constant rotation for a total of about 160,000 troops. That is just under half of the entire Russian army (the Russian Ground Force). In this article, I update the occupation troop-to-task assessment, accounting for President Putin's more ambitious invasion through Kyiv in the north and Odessa in the south.

This updated estimate is based on what I perceive to be four bare-minimum tasks the Russians will need to perform: (1) secure the perimeter of their occupied area from infiltration; (2) secure key nodes like power stations and communications centers in urban areas; (3) secure key roads and railways to keep open interior lines of communication; and (4) secure the population and conduct civil-military and counterinsurgency operations. Using a new, probable limit of advance just west of the Dnieper River and north of Odessa, I estimate that the Russians would need to deploy 168,000 occupation troops and keep another 168,000 in constant rotation for a total of 336,000 troops. That constitutes over 95% of the entire Russian Ground Force of approximately 350,000 personnel, not including available Russian airborne, special operations, or National Guard troops.

All estimates that follow are based on the troop-to-task baseline estimates here. I used the same population data and other cited sources to build the present estimate. As I did in the first estimate, I used Google Earth Pro for all linear and area calculations. All caveats that applied to the first article apply to this article. Estimating troop-to-task is an informed subjective activity. Numbers presented here are estimates only and should not be used for military planning purposes.

Task 1: Secure the Perimeter of the Occupied Territory

In the likely event that the Russians defeat the Ukrainian defenders, the war probably will not end. Ukrainians probably will continue to fight as insurgents against the Russian occupiers. As of early March 2022, hundreds of millions of dollars in Western military equipment are flowing into Western Ukraine and into the combat zone. During an occupation, these contributions likely will continue in support of an insurgency. Russia will be forced to secure the perimeter of the occupied territory to try to prevent infiltrations and protect their occupying army. Figure 1, below, shows the estimated occupied territory and the perimeter.

Figure 1: Securing the 2,950-Kilometer Linear Perimeter

Ben Connable

From the Belarusian border north of Kyiv to the Russian border east of Mariupol, the perimeter of the estimated occupied territory is approximately 2,950 kilometers in length. Using the baseline calculation of one battalion of approximately 540 troops to secure each 80-kilometer section, perimeter security would require 19,980 (rounded up to +20,000) front-line troops. Because these troops need staff and logistics support, this amounts to two reinforced Russian divisions with 2,400 staff, logistics, and aviation troops each (+ 4,800) and expanded coastal security (+1,500 troops) plus an army headquarters (1,000) for a Task 1 subtotal of 27,300.

Task 2: Secure Key Nodes in Urban Areas

If the Russians intend to hold or even annex the territory they will have seized, they will eventually need to provide food, water, power, sanitation, healthcare, and other essential services. Insurgents will seek to target some of this infrastructure to undermine the occupation. There may be approximately 26 million people living in this occupied zone. Given the uncertainty of Ukrainian population estimates, population displacement from the war, and the relatively stable situation in Crimea (~2 million people), I use 19 million as a round population estimate. There are 22 major urban areas in the occupied zone.

Figure 2, below, shows the urban areas requiring key node security. Major urban areas like Kyiv, Kharkiv, and Odessa will probably have more than five key nodes, so this should be considered a low estimate.

Figure 2:Securing Key Nodes in Urban Areas

Ben Connable

In the original troop-to-task analysis I estimated that each urban area would have five key nodes requiring security, that each node would require 145 troops, and that every three nodes would require another 140 troops. Therefore, key node security would require 25,900 troops (22 nodes x 5 nodes = 110, 110 x 145 troops = 15,950 + 5,180 staff = 21,130 + 4,800 division staff and attachments = 25,900, rounded down). The running occupation subtotal for Tasks 1 and 2 is 53,200 (27,300 + 25,900 = 53,200).

Task 3: Secure Key Roads and Railways

Keeping an occupation force fueled, fed, and supplied with ammunition and spare parts for vehicles, radios, and other equipment requires freedom of movement throughout the occupied area. Ukrainian insurgents will probably work to disrupt logistics traffic, ambush convoys, plant mines and other explosive devices, and otherwise disrupt Russian freedom of movement. Securing lines of communication requires setting up checkpoints and running patrols along the routes most often used by occupying forces. Some risk must be taken on secondary roads, all of which can be used by insurgents to infiltrate and conduct attacks.

Figure 3, below, shows the 7,255 kilometers of secured road and railway in dark green, as well as a number of unsecured secondary roads located throughout the occupied territory.

Figure 3: Securing Road and Railway in the Occupied Territory

Ben Connable

I estimated that each 40-kilometer section of secured road and rail would require 63 Russian troops, the equivalent of two platoons or a reduced company. Working from a map analysis of the occupied territory, I estimated the Russians would need to secure 7,255 kilometers of road and railway. This breaks down into 181 sections, 63 troops per section (+11,403), with 140 battalion staff for every 400 troops (+4,060), plus two division staffs and attachments (+4,800) for 20,300 troops, rounded up. The running occupation subtotal for Tasks 1, 2, and 3 is 73,500 (27,300 + 25,900 + 20,300 = 73,500).

Task 4: Secure the Population and Conduct Counterinsurgency

If Russia’s invasion succeeds, the Russian Federation will assume de facto responsibility for the well-being of approximately 19 million people. That is equivalent to the population of the American states of New York or Florida. It is also approximately 14% of the current estimated population of Russia. In terms of landmass and population, this will be by far the largest occupation attempted by the Soviet Union or the Russian Federation since the Soviet occupation of Eastern Europe in the years after World War II. Much of the infrastructure needed to sustain the Ukrainian population in the occupied zone is presently being destroyed. Occupation officers will find themselves responsible for supporting millions of people and rebuilding their cities while fending off an active, NATO-backed insurgency. A dedicated joint civil-military and counterinsurgency force will be needed to give the Russians any hope of successfully managing these tasks.

Figure 4, below, shows the Ukrainian State Statistics Committee estimated populations for each Ukrainian oblast, or state, within the occupied territory.

Figure 4: Estimated Population Within the Occupied Territory by Oblast

Ben Connable

In the original troop-to-task estimate, I used the population estimate for Kharkiv oblast as a baseline for analysis. I separated Kharkiv into 10 sections of approximately 173,000 people each and identified the need for a reinforced Russian motorized infantry battalion of 650 soldiers to secure each section. Using this same baseline estimate, Russia would need to assign 110 battalions (+ 71,500 troops) within eight divisions (+ 22,400 division staff and attachments) and one army group (+1,000) for a total of 94,900 troops. Total occupation troop cost for all four tasks is 168,000 (27,300 + 25,900 + 20,300 + 94,900 = 168,400, rounded down). Another 168,000 troops would need to be kept in constant rotation for occupation duty, tying down approximately 336,000 Russian troops for what may be a multi-year occupation.

If this occupation troop to task estimate seems high, points of comparison might be useful. When the Soviet Union began its unsuccessful occupation of Afghanistan in 1979, Afghanistan had a population of approximately 13 million people. At the peak of its counterinsurgency operation, the Soviets had approximately 100,000 troops in Afghanistan supported by an equivalent number of Afghan troops and militiamen. At the end of 2011, two years before the Islamic State seized one-third of the country, the U.S.-led coalition, and the Iraqi security forces fielded approximately 750,000 troops and police to control approximately 30 million people. Applying the oft-referenced 2% troop-to-population ratio—an approach I advise against—suggests the need for 380,000 troops in Ukraine with another 380,000 troops in constant rotation for a total of 760,000 Russian occupation troops.

Russia’s Advantages and Disadvantages in Occupation

Russia has at least two distinct advantages and faces at least seven significant disadvantages in a prospective occupation. Proximity to the Russian border and relatively flat terrain provide good access for logistics and air support, and Russian intelligence officers have a good understanding of Ukrainian language and culture. They will not face the same cultural challenges the United States faced in Vietnam, Iraq, and Afghanistan.

However, Russia’s aggressive destruction of Ukraine’s infrastructure will make the occupation costly and onerous. Based in part on this RAND examination of insurgency dynamics, the Russians will also be challenged by the existence of a large sanctuary in western Ukraine; strong external support for the insurgency; the probable emergence of a hybrid rural-urban insurgency (which are particularly difficult to dig out); the probable lack of a legitimate partner government in Kyiv; probable lack of any reliable partner security forces to defray the cost of all of these occupation tasks; and, primarily, the very low likelihood that the Russians will seek or be able to address the root causes that will drive the insurgency. Russians destroying Ukraine today are fueling the will to kill Russian soldiers tomorrow and for years to come.

Dr. Ben Connable is a senior nonresident fellow at the Atlantic Council and adjunct professor of security studies at Georgetown University.