The battlecruisers, brainchild of Admiral Sir John Fisher, 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 lead to their inclusion in the battlefleet as a fast squadron of capital ships. This book traces the development of Fisher's original idea into the first battlecruiser Invincible of 1908, through to the 'Splendid Cats' of the Lion class, and culminating in HMS Hood in 1918, the largest warship in the world for the next twenty years. The origins of the unusual 'light battlecruisers' Courageous, Glorious and Furious, later to find fame as aircraft carriers, are also covered. The problems the class suffered are also examined, including the catastrophic loss of three battlecruisers at Jutland in 1916. The developmental history of the battlecruisers is complemented by chapters covering machinery, armament and armour and a full listing of important technical information. With its superb plans and drawings and entirely original research, this book is essential reference for all naval historians, enthusiasts and modelmakers with an interest in the most charismatic and controversial warships of the battleship era.