In general, the US and the European countries were focusing more and more on naval power in the 19th century, thanks to a groundbreaking book by US Captain Alfred Thayer Mahan called The Influence of Sea Power Upon History. In this book, widely read on both sides of the Atlantic, Mahan convincingly argued that the most powerful nations of the previous eras had always been the ones with the most powerful navies, from the Athenians on. Britain, which had controlled the seaways for much of the 19th century, was a prime example. Now, after reading Mahan's books, European and American leaders sought to build strong navies to protect their countries' interests and trade around the world. The US and other countries, especially Germany, started building world-class navies during this time thanks largely to Mahan's influence.
Why was Roosevelt so eager to have Dewey attack the Spanish fleet in the Philippines, a move that certainly would not help in the liberation of Cuba? Furthermore, why would the cautious McKinley ever approve such a move? The reason involves Mahan's theories yet again. In order to protect trade and influence throughout the world, Mahan advocated a series of island coaling stations throughout the world. (Since US ships ran on coal at the time, they needed places to stop and refuel) Roosevelt and McKinley hoped taking the Philippines from the Spanish would provide the US with a coaling station to help the US Navy patrol in the Far East, keeping Asian markets open to US traders and merchants. Here, with the move against the Spanish Philippines, the initial goal of liberating Cuba expressed in the Teller Amendment seemed to be giving way to a desire for imperialist expansion.