Why interventions such as Vietnam or Afghanistan fail to achieve their objectives is naturally a consequence of a vast range of factors. Ideology, psychology, strategy, policy, resources and timing matter hugely. As does the enemy’s own agency of course. But in addition to such weighty matters sits the perennial question of whether the external actors in each case truly understood enough of the countries and societies that they were intervening in to give their designs the maximum prospect of success. To that end, this book examines five particular case studies: The British on the North-West Frontier 1919–39, the French campaign in Algeria 1954–62, the US pacification campaign in Vietnam 1966–72, and US-led coalition operations in Iraq 2003–11, and Afghanistan 2001–present. In the context of the themes and issues highlighted so far, these examples are intended to provoke deeper thinking about the way in which forms of knowledge and understanding are brought to bear upon the process of armed intervention.