A decade ago, I was a U.S. diplomat serving in Warsaw, Poland. I had a close group of Polish friends who, while not in the field of foreign affairs, had a strong fear of Putin’s Russia. They were concerned his aggression and resentment would lead him one day to launch war again in Europe. I dismissed their concerns as a Cold War hangover. Poland then seemed so prosperous and at peace, and Russia so weak compared with the EU. The 2008 invasion into Georgia seemed a far cry from a threat on Western Europe. Then came the 2014 invasion of Crimea, the 2016 interference in our own elections and year…