The Baltic nations of Latvia, Lithuania, and Estonia, along with Poland, Slovakia, Romania, and Bulgaria, are all watching Vladimir Putin’s military buildup in eastern Europe with great unease. Each of them was controlled by Russia during its previous incarnation as the Soviet Union, and none of them wishes to return to that subjugation. That’s why they originally sought membership in the North Atlantic Treaty Organization, and have increased their own defense spending to meet, and in some cases surpass, the 2-percent-of-GDP goal that the alliance first agreed upon in 2014. NATO membership brings with it the guarantee of security that the U.S. has provided to Europe for 70 years, and with an aggressive Russia looming to the East, security is very much a concern.

There are, however, several problems with this calculation. First, the botched withdrawal of American forces from Afghanistan and the abandonment of American citizens and loyal allies there have dealt a significant blow to the U.S.’s credibility everywhere else. Second, the U.S. Army, the linchpin of security in Europe, largely returned to the United States years ago. Finally, due to Russia’s investments in anti-access area-denial weapons at its enclave in Kaliningrad, the U.S. Navy can no longer get Army units to Europe in time to blunt a Russian onslaught should one occur. Russia has amassed a force of over 100,000 troopsalong its border with Ukraine, including formations of heavy artillery, armored troop carriers, and main battle tanks. It has also already initiated cyber-attacks against critical infrastructure in Ukraine. If Russian forces should suddenly roll over Ukraine and then position themselves to threaten the Baltic nations, Poland, Romania, and Bulgaria, NATO will find it difficult to respond quickly.

As part of the European Defense Initiative, the U.S. has built a cache of pre-positioned ordnance, including enough equipment for an armored brigade, in Poland. The men needed to make use of that equipment and man the tanks and armored personnel carriers would be flown in from the United States at the first sign of trouble. Additionally, NATO has established a response-force brigade (5,000 personnel) and enhanced forward-presence battalions (400 personnel), but it must be admitted that these will serve as nothing more than a speed bump if Russia initiates a rolling start and then sprints across Ukraine, a nation that is just under 800 miles wide and possesses modern road and rail systems. Should they meet with minimal resistance, Russia’s armored forces, with adequate logistical support, could cross Ukraine and be on NATO’s doorstep in ten days or less. They would confront a NATO ill-prepared for the threat they posed.

Over the past 20 years, NATO nations have decreased their investments in mobile armor and artillery, by far the most expensive of the ground forces, and the United States has not only followed this path but also pulled its last permanently based armored unit out of Europe. The U.S. Army, which once fielded numerous armored divisions of up to 12,000 to 16,000 men each, now retains but one, although there are smaller armored brigade combat teams (BCTs) incorporated into the six standing infantry divisions and one mountain division that remain in the active force. The simple truth that few wish to reckon with is that, aside from air-power assets — the F-35 would most certainly get its baptism-by-fire against Russia’s fighters and its advanced S-400 missiles — under the best circumstances only one or two U.S. armored brigades would be available during the first 72 hours. Thus, only 10,000 men, some transported by air to join up with pre-positioned equipment and others previously assigned to the region as part of a rotational force, would be available to aid our European allies and blunt a rolling Russian assault.