Despite the shock of the Russian invasion, the tone was measured and matter of fact. There was a sense of purpose, a recognition that this could be, if the opportunity was taken, NATO’s moment to show how relevant it still was. After all, this was the very sort of scenario that the Alliance had been formed to confront sixty-five years earlier. Conversely, fail to match the moment and there was a real risk that this might be the point that NATO’s inherent weakness—the requirement for all twenty-eight member states to agree on a course of action—was laid bare for all to see.

Which was it to be?

I remember well the air of unreality as the detailed contents of Putin’s Kremlin speech were analyzed for us by the Operations Chief, a US airborne forces major general, a veteran of America’s wars of the past decade and a man not given to hyperbole. He quoted the sometimes bizarre, always hyper-nationalistic, words of the President: “We have all the reasons to believe that the policy of containment of Russia which was happening in the eighteenth, nineteenth, and twentieth centuries is still going on.” Followed by Putin’s chilling warning to the West: “If you press the spring, it will release at some point; something you should remember.” It ended with the unequivocal statement that Russia and the Ukraine were “one nation” and “Kiev is the mother of Russian cities.”

As I listened, the implications were clear. The annexation of Crimea, and the President’s vow to reunite “Russian speakers” in the former republics of the Soviet Union under the banner of Mother Russia, was little different from Hitler’s annexation of the Sudetenland in 1938. Would future historians judge this as our generation’s Rhineland and Sudetenland moment? And to continue the analogy to its logical conclusion, would an implicit Russian attempt to reincorporate the Baltic States—with their significant Russian-speaking minorities—into a new Russian empire in a couple of years’ time be our Poland? My answer was an emphatic “yes.”—if NATO, under US leadership, failed to step up to the mark.

In the following days we watched the continued Russian build-up of troops on both the borders of Ukraine and the Baltic States. This was not in the modern NATO script or the way “the West”—meaning broadly the US, Canada, Europe, Australia, and New Zealand—viewed the world either.

Eminent western military thinkers were even now proclaiming the end of state-on-state industrial war. But if my passionate study of history has taught me anything, it is to take no apparent certainty for granted, together with our inability to learn the lessons of the past. I felt as if I were back at the British Army Staff College in the Cold War days of the late 1980s. We were once again talking of Russian tank armies and airborne divisions and calculating where and when they might attack across the border into Ukraine.