On March 7, 1936, Hitler sent German troops into the Rhineland, violating the Treaty of Versailles. It was a complete bluff if France had responded, he would have retreated. But France did nothing. Britain did nothing. The League of Nations did nothing. Hitler learned he could get away with aggression. Three years later, World War II began. This is a story about how the desperate desire to avoid war made war inevitable and why appeasement, born from good intentions and terrible trauma, became one of history's costliest mistakes.