Britain's Channel defences have played a vital role in the history of this country and its people. This book reveals the minds and mechanics behind the military strategy. When was Britain in most danger of being invaded? How well protected was the southern coastline? What measures were taken against these threats? From the Spanish Armada to the Nazi Blitzkrieg, this guide examines the developing naval and military responses to the threat of invasion and highlights the places of most strategic importance and interest along the southern coast. It examines the plans to invade Britain and how they were beaten back, and discusses the importance of the naval bases and dockyards of Portsmouth, Plymouth, Chatham and Portland. It also reveals how emergency measures could be brought into play on the beaches and the role of the Martello Tower system.