My grandfather was 13 years old the day the Munich Agreement was signed in 1938. The pact ceded Czechoslovakia’s strategic Sudetenland region to Germany, in order to head off a German invasion of the country. Britain and France, with the encouragement of the United States, negotiated the agreement directly with Hitler. The Czechs were not invited to weigh in on the dismemberment of their country. British Prime Minister Neville Chamberlain lauded the agreement, saying, “I believe it is peace for our time.” Those words would haunt the apocalypse that followed.

My grandfather likely knew little of what was happening in Czechoslovakia, and almost certainly didn’t know that events there would change the course of his life. Hitler, who had no intention of stopping at the Sudetenland, conquered the rest of Czechoslovakia the following year. As the rest of Europe fell to Nazi armies, and crimes against humanity multiplied in their wake, the error of Munich became tragically clear.

Seven years later, my grandfather was in a B-24 bomber over Austria, on a mission to bomb an oil refinery supplying Hitler’s war machine. Anti-aircraft shells burst black everywhere around his plane. Suddenly, a German shell blew a hole through the wing behind one of the plane’s engines. The propeller slowed, then stopped, fuel hemorrhaging through the wound in the wing. As their plane slowed and fell out of formation, my grandfather and his crew realized in horror that they would not be returning to the safety of their base.

It was not inevitable that American boys would be fighting for their lives in the skies over Nazi-occupied Europe in 1945. But in their desperation to avoid a smaller war over Czechoslovakia, Western leaders had ensured that war would consume the world, with America paying its share of the butcher’s bill.

Americans like to think that the concerns of Europe are not our own. It is an assumption that cost many American lives in the last century. Our desire to stay out of Europe’s quarrels in the 1930s and 1940s did not stop Germany from conquering or besieging our friends and trading partners. It did not stop German submarines from bringing war to our shores. It did not stop Hitler from declaring war on us. The desire to ignore European affairs is even more futile in a smaller modern world, in an era of hypersonic missiles and cyberattacks.

On Feb. 28, the president and vice president berated Ukrainian President Volodymyr Zelensky for risking World War III. Yet they are engaged in exactly the behavior that guaranteed the last world war: offering an aggressive dictator territorial concessions, with or without Ukrainian consent, in the naive belief that he will be satisfied.

Putin’s war in Ukraine is only the latest Russian war of aggression against a neighbor in recent decades. Appeasing him will only accelerate his appetite for a larger war in Poland, the Baltics, Scandinavia and beyond. It is a war into which the United States would be inevitably dragged.

My grandfather was lucky. The pilot of his plane skillfully crash landed in Yugoslavia, where partisan fighters helped the crew get back to Allied lines. It was an experience that profoundly affected him for the rest of his life. When he and his crew got back to their base in Italy, they were put right back in the air to fly more bombing missions, to risk it all again and again.

Leaders in the West did not stand strong against Hitler when they had the chance. My grandfather’s generation had to stand against him when they had no choice.

Where will America’s 13-year-olds be in seven years? And where today are the adults who should know that the consequences of appeasing a madman will fall on our children?