By the district

NATO chief Anders Fogh Rasmussen claimed that 40,000 Russian troops are massing close to the Ukrainian border. Satellite images seemed to confirm the build-up of hundreds of armored vehicles and artillery pieces supported by helicopters and Su-27, Su-24 and MiG-31 fighter jets.

That’s an alarming force … on paper. But FOI took a different approach in its report. Instead of just looking at the raw numbers of troops Russia has at its disposal, the researchers analyzed specific military units that could take part in an extended campaign.

There’s a simple enough reason for this way of thinking. Different units have different roles, responsibilities and capabilities. Some are dedicated to defending Russian territory far away from the Ukrainian border and would likely not take part in an invasion—at least not at first. A unit-by-unit review gives a more accurate picture of the Kremlin’s capabilities.

First, the Kremlin organizes its forces in four huge military districts, each responsible for defending hundreds of thousands of square miles of territory. There are typically two field armies in each district, with each army made up of several divisions.

The Southern District oversees Russian units in the Caucasus, where Moscow is trying to suppress a low-boil Islamic insurgency. The Western District is responsible for defending western and northwestern Russia, including St. Petersburg and Moscow. The Central District protects a wide swath of territory from the Kazakh border deep into Siberia.

Russia’s armies and possible invasion zones. Swedish Defense Research Agency/Ministry of Defense illustration

Each district has two armies each, for a total of six armies with varying capabilities. In the Southern District, there are the 49th and 58th Armies. The Western district includes the 20th and 6th Armies. In the Central District, the 41st and 2nd Armies.

According to the FOI, if Russia decides to expand its invasion beyond Crimea, it would need at least two or three armies “first to push into territory but probably also over time to secure that [which was] taken.”

The most likely forces for this job are the 2nd and 20th Armies. Unlike the Southern District armies, these are neither committed to reinforcing Crimea, nor are they fighting insurgents in the Caucasus.

The 2nd is a particularly good candidate. It’s capable of fielding multiple motorized infantry brigades. These are good for offensive operations.

The 2nd Army also took part in recent exercises along the Ukrainian border—meaning it should be in a high state of readiness. Its sister army in the Central District, the 41st Army, is based too far to the east.

The 20th Army, on the other hand, is normally located near Moscow and includes two tank brigades and two motorized infantry brigades. It’s “the strongest ground-force unit” in the district, FOI states. The 6th Army would likely stay close to the big Russian cities to protect them from either a foreign attack or uprising.

All told, this means Russia has “seven to nine maneuver brigades” ready to invade within 10 days of the Kremlin giving the order. That’s roughly 40,000 troops, or the same amount Rasmussen estimated were in positions across the Ukrainian border.

“The sizable force would nevertheless hardly be enough for securing land communications to Transnistri a— by holding on to all of Ukraine’s Black Sea Coast — let alone holding to eastern Ukraine in the face of Ukrainian armed resistance,” FOI concludes.