Recent panicky talk of a third world war seems a tad overblown. Yet the specific threat posed by Russia’s aggressive, revisionist regime to eastern Europe is real and growing. As in the past, Poland is on the frontline of a battle for Ukraine that could easily spread. Scrambling to shore up defences, the UK and European Nato states must decide: is this 1920 or 1939? As all Poles know, the Battle of Warsaw, 104 years ago this August, ended in Marshal Józef Pi?sudski’s famous victory over the invading Red Army, which secured their country’s independence. They called it the “Miracle...