How do we plan under conditions of uncertainty? The perspective of military planners is a key organizing framework: do they see themselves as preparing to administer a peace, or preparing to fight a future war? Most interwar volumes examine only the 1920s and the 1930s. This new volume goes back, and forward in time, to draw on a greater expanse of history in order to tease out lessons for contemporary planners. These chapters are grouped into four periods: 1815-1856, 1871-1914, 1918-1938, and post-Second World War. They progress from low-tech to high-tech concerns, for example, the first period examines armies, while the second period examines navies, the third assesses navies combined with air forces, and finally for the Kaiser chapter explores nuclear issues and decision-making.