Ever since humans began to live together in settlements they have felt the need to organise some kind of defence against potentially hostile neighbours. Many of the earliest city states were built as walled towns, & during the medieval era, stone castles were built both as symbols of the defenders` strength & as protection against potential attack. The advent of cannon prompted fortifications to become lower, denser & more complex, & the forts of the eighteenth & nineteenth centuries could appear like snowflakes in their complexity & beautiful geometry. Without forts, the history of America could have taken a very different course, pirates could have sailed the seas unchecked, & Britain itself could have been successfully invaded. This book explains the history of human fortifications, & is beautifully illustrated using photographs, plans, drawings & maps to explain why they were built, their various functions & their immense historical legacy in laying the foundations of empire.