Complex sentence: 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.
Split into simpler sentences: Mahan argued for a universal principle of concentration of powerful ships in home waters and he minimized strength in distant seas. However, Fisher reversed Mahan by using technological change to propose submarines for defense of home waters and mobile battle cruisers for protection of distant imperial interests.