ON OCTOBER 21, 1805, Admiral Horatio Nelson and his British fleet wiped out a combined French and Spanish fleet at Trafalgar, ushering in decades of British naval superiority. In 1828, following a victory over the Ottoman Navy at Navarino in 1827 and conscious of their global leadership in sea power, the lords of the British Admiralty issued a regulation discouraging the development of steam-powered boats with the logic that any naval technological innovations would only threaten Britain's naval predominance. These regulations controlled the British Navy for thirty years; in 1851 the British Navy still looked like it had for much of the last three centuries, dominated by ships of the line. After the introduction of the great French ironclad, La Gloire, in 1858, and reports of the epic 1862 U.S. naval ironclad clash between the Monitor and the Merrimack, however, the British rapidly shifted their ship production to iron and then steel warships propelled by steam instead of sail. But most other elements of naval strategy remained the same; doctrine, education, organizational structure, promotions, recruitment, and training all looked almost exactly the same in the 1880s as they had at Trafalgar.
Yet in the short period of time that followed, in the run-up before World War I, the greatest naval power in the world overhauled everything from its doctrine and training to force structure. This shift, launched in 1906 with the HMS Dreadnought as its public face, represents one of the only cases of a dominant global military power self-consciously reshaping the core competencies that had guaranteed its success without ever losing a battle. This shift, sometimes called the Fisher Revolution after the fiery leadership of First Sea Lord John Fisher, but called the battlefleet warfare innovation in this book, helps to define why understanding the diffusion of major military innovations is essential to grasping the development, spread, and use of military power in general.
The introduction of the HMS Dreadnought and the organizational changes accompanying battlefleet warfare drove substantial changes in the way that the major naval powers designed and planned for warfare. On the technological side alone, navies around the world froze their construction plans for over a year as they attempted to digest what the Dreadnought, with its uniform caliber guns and fast propulsion system, would mean for naval warfare. The rising cost per unit of dreadnought-style ships also meant that the total number of capital ships possessed by a navy declined even as the relative power of the