The brainchild of Admiral Sir John Fisher, battlecruisers combined heavy guns and high speed in the largest hulls of their era. Conceived as super-cruisers to hunt down and destroy commerce raiders, their size and gun-power led to their inclusion in the battlefleet as a fast squadron of capital ships. This book traces in detail the development of Fishers original idea into first battlecruiser Invincible of 1908, through to the Splendid Cats of the Lion class, and culminating in HMS Hood in 1920, the largest warship in the world for the next twenty years. The origins of the unusual light battlecruisers of the Courageous type are also covered.