Geopolitical conditions influence all strategic behaviour - even when co-operation among different kinds of military power is expected as the norm, action has to be planned and executed in specific physical environments. The geographical world cannot be avoided, and it happens to "organized" into land, sea, air and space - and possibly the electromagnetic spectrum including "cyberspace". Although the meaning of geography for strategy is a perpetual historical theme, explicit theory on the subject is only 100 years old. Ideas about the implication of geographical, especially spatial, relationships for political power - which is to say "geopolitics" - flourished early in the 20th century. Divided into theory and practice sections, this volume covers the big names such as Mackinder, Mahan and Haushofer as well as looking back at the vital influence of weather and geography on naval power in the long age of sail (16th-19th centuries). It also looks forward to the consequences of the revival of geopolitics in post-Soviet Russia and the new space-based field of "astropolitics".