naval forces not strong enough to do both. Mahan argued for a universal principle of concentration of powerful ships in home waters and minimized strength in distant seas, while Fisher reversed Mahan by utilizing technological change to propose submarines for defense of home waters and mobile battle cruisers for protection of distant imperial interests. German Mahan was initially introduced to the German navy by the strategist Ludwig Borckenhagen, in a series of influential papers. Subsequently, his name became a household word in the German navy, as Kaiser Wilhelm II ordered his officers to read Mahan, and Admiral Alfred von Tirpitz (1849–1930) used Mahan's reputation to build a powerful surface fleet. French The French at first adopted Mahan's theories. French naval doctrine in 1914 was dominated by Mahan's theory of sea power and therefore geared toward winning decisive battles and gaining mastery of the seas. But the course of World War I changed ideas about the place of the navy, as the refusal of the German fleet to engage in a decisive battle, the Dardanelles expedition of 1915, the development of submarine warfare, and the organization of convoys all showed the navy's new role in combined operations with the army. The navy's part in securing victory was not fully understood by French public opinion in 1918, but a synthesis of old and new ideas arose from the lessons of the war, especially by admiral Raoul Castex (1878–1968), from 1927 to 1935, who synthesized in his five-volume Théories Stratégiques the classical and materialist schools of naval theory. He reversed Mahan's theory that command of the sea precedes maritime communications and foresaw the enlarged roles of aircraft and submarines in naval warfare. Castex enlarged strategic theory to include nonmilitary factors (policy, geography, coalitions, public opinion, and constraints) and internal factors (economy of force, offense and defense, communications, operational plans, morale, and command) to conceive a general strategy to attain final victory. United States Locating a sufficient supply of guano that enabled the radical incline of refertilizing American farmlands that would otherwise become desolate from nitrogen deficiency through successive farming year-on-year was a contextualising element to Mahan's work. With a Peruvian (and British) monopoly on guano across South American islands, this pushed the US into searching and securing alternative islands that fed into Mahan's goal of creating sea "highways" between land. To expedite this process, the US Congress had previously passed the Guano Islands