The games’ findings are unambiguous: As currently postured, NATO cannot successfully defend the territory of its most exposed members. Across multiple games using a wide range of expert participants in and out of uniform playing both sides, the longest it has taken Russian forces to reach the outskirts of the Estonian and/or Latvian capitals of Tallinn and Riga, respectively, is 60 hours. Such a rapid defeat would leave NATO with a limited number of options, all bad: 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.

Fortunately, avoiding such a swift and catastrophic failure does not appear to require a Herculean effort. Further gaming indicates that a force of about seven brigades, including three heavy armored brigades—adequately supported by airpower, land-based fires, and other enablers on the ground and ready to fight at the onset of hostilities—could suffice to prevent the rapid overrun of the Baltic states. While not sufficient to mount a sustained defense of the region or to achieve NATO’s ultimate end state of restoring its members’ territorial integrity, such a posture would fundamentally change the strategic picture as seen from Moscow. Instead of being able to confront NATO with a stunning coup de main that cornered it as described above, an attack on the Baltics would instead trigger a prolonged and serious war between Russia and a materially far wealthier and more powerful coalition, a war Moscow must fear it would be likely to lose.

Crafting this deterrent posture would not be inexpensive in absolute terms, with annual costs perhaps running on the order of $2.7 billion. That is not a small number, but seen in the context of an Alliance with an aggregate gross domestic product in excess of $35 trillion and combined yearly defense spending of more than $1 trillion, it hardly appears unaffordable, especially in comparison with the potential costs of failing to defend NATO’s most exposed and vulnerable allies—that is, of potentially inviting a devastating war, rather than deterring it.