Why did Volodymyr Zelensky doubt that Russia was preparing a full-scale invasion of Ukraine in 2022? Why did British Prime Minister Neville Chamberlain decide to “do business with Herr Hitler” in Munich in 1938? This pithy book showas that strategy-making is a tricky business, marred by bias, irrationality, bureaucratic politics, colliding government interests, and complex procedures and structures. Assessing our adversaries as ‘rational actors’ is a dangerous game that can lead to flawed and, on occasions, catastrophically bad decisions. This book explains why.