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? And how was it that Israeli elites dismissed intelligence warnings of the Hamas attack in 2023? Had they not learned their lesson from the Egyptian-Syrian attack on Yom Kippur fifty years earlier?

In all these cases, smart decision-makers misjudged their adversaries, largely because they failed to understand how their enemies' actions and strategies were shaped by different values and beliefs to their own. We may think such beliefs are irrational merely because we do not share them. They may appear confusing and ill-judged. But as Beatrice Heuser ably shows in this pithy book, 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.