For many people Martello towers are remembered from holidays at English seaside resorts. This book shows how they were part of a revolution in defensive technology in the 19th century which cost as much in real terms as our nuclear deterrent does now. It also follows the spread of Martello towers throughout the British Empire, with photographs, many by the author, of surviving examples around the world. Overall, it gives a fascinating glimpse of how some military problems of the early nineteenth century were tackled.