NATO has no way of stopping a Russian conventional invasion of Estonia and Latvia short of nuclear war, according to a new RAND Corporation study.

That's not surprising in itself. Russia has one of the world's most powerful militaries, and can field vast armies compared to the Baltic states with their small populations. Not only are the Baltic armies small, but NATO reinforcements would be slow coming in the early hours of a conflict, allowing Moscow to quickly bypass or destroy the alliance's defenses.

What is surprising, or at least not discussed enough, is how quickly Russia would steamroll the Baltic states — and that has the study's authors David Shlapak and Michael Johnson worried.

The study relies on a series of tabletop war simulations of a surprise Russian ground invasion directed at the capitals of Estonia and Latvia. U.S. military officers and RAND analysts played the role of the combatants. They found Russian forces will have "eliminated" NATO resistance and be "at the gates of or actually entering Riga, Tallinn, or both between 36 and 60 hours after the start of hostilities."

"Such a rapid defeat would leave NATO with a limited number of options, all bad," Shlapak and Johnson wrote.

"A bloody counteroffensive, fraught with escalatory risk, to liberate the Baltics; to escalate itself, as it threatened to do to avert defeat during the Cold War; or to concede at least temporary defeat, with uncertain but predictably disastrous consequences for the alliance and, not incidentally, the people of the Baltics."

Tabletop wargaming is an interesting choice for the study. Although games are not perfect and can only test possibilities, as opposed to an actual war, professional armies have relied on them for centuries. This is just a game, but one with a level of detail and scale that's difficult to capture outside of a real-life military exercise.

Here are some of the details. Assuming NATO has a week to detect a coming invasion, the alliance could deploy an equivalent of 12 maneuver battalions in the Baltic states. This includes the 173rd Airborne Brigade Combat Team rushed from Vicenza, Italy, but no main battle tanks. Poland — which has the largest tank force in Europe west of the Bug River — would be "assumed to be committed to defend the [Polish] national territory" and blocking Russian forces from moving south from Kaliningrad.

However, Russia could mass the equivalent of 22 maneuver battalions, including four tank battalions and large amounts of artillery from its Western Military District. Russia would also have an advantage in the air, with 27 squadrons of fighters and bombers compared to 18.5 NATO squadrons. While able to challenge Russian aircraft, the NATO planes could not quickly establish air superiority. Russian combat planes would then create "bubbles" of undefended airspace to launch "massed waves of air attacks."

There's an important lesson here — though Russia cannot challenge the United States or NATO globally, it can do so locally … and win.

To be sure, NATO has additional forces including at least two-dozen M-1 Abrams tanks and 30 M-2 Bradley fighting vehicles stored in Grafenwoehr, Germany. But RAND estimates those tanks need at least 10 days to organize and travel. Not enough time before a Russian victory.

That's bad news for the soldiers facing an onslaught. Light infantry could slow an invasion by digging into the Baltic capitals, but the final result would be similar — a Russian victory except now at a high cost to the urban population.

There's a worse fate for ground troops outside the cities, according to the study. "They proved unable even to retreat, since they literally could not outrun their pursuers," the RAND researchers noted.

As to what NATO might do next, it's worth reading the study in full. Reinforcing NATO's eastern flank may deter the Kremlin, if it considered an attack. Beefing up Baltic armies with liberal supplies of anti-tank missiles would help delay, but not stop, a Russian assault.

The main problem is that geography favors Russia. In the days after an invasion, the alliance would have to first mass its own forces and conquer Kaliningrad, a Russian enclave bordering Poland which could flank any counter-attack … before facing the bulk of Russia's Baltic combat power.

But remember — it's just a game.

And because a Russian victory, at least in the short term, is possible doesn't mean the Kremlin would ever invade. Article 5 of the Washington Treaty obligates NATO to defend its allies, including Estonia and Latvia, if they came under attack. That could plunge Russia into a wider and far more destructive war it might eventually lose, but it could also set off a chain of events ending in a nuclear exchange.

Which is why if Russia were to do it, it would want to do so quickly, presenting NATO with the option of … doing nothing.

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