Even though the Battle of Manila had little direct relation to freeing Cuba from Spanish rule, Americans were excited by Dewey's sudden victory over the larger (but older) Spanish Navy at Manila. However, Dewey had no troops, and without troops, the invasion of Manila could not begin. The US Asiatic Squadron had to wait for months in the sweltering heat of Manila Harbor, waiting for American troops to arrive for a ground assault. While they waited, other European fleets sailed near Manila, especially the German and British fleets. Although not involved in the war, both countries sent ships claiming that they wanted them there to evacuate Germans and Britons in the event of serious fighting. However, the German fleet also sought to harass Dewey and intimidate the US. The British, on the other hand, wanted to offset German intimidation in order to foster better relations between Britain and America. At this time, Britain was aware of America's rapid increases in power due to industrial growth, and was hoping to pave the way for future alliances.
Finally, after Dewey's ships had waited for months, US ground troops arrived in the Philippines. The US troops allied with the Filipino guerillas to fight against the Spanish. The guerillas were led by Emilio Aguinaldo, a Filipino nationalist who the Spanish had exiled, and who Dewey brought back to help unify the people against their Spanish overlords. The Filipinos saw the US as liberators, and gladly fought alongside them. On August 13, 1898, US troops, aided by Aguinaldo's guerillas, captured Manila.
War in the Philippines proved to many Americans the importance of another set of Pacific islands, the Hawaiian Islands. Hawaii, considered the "crossroads of the Pacific" might be used as a coaling station to help supply the US Navy in future operations in the Pacific. To be honest, Hawaii could have easily worked as a coaling station without formal annexation, since American businessmen essentially controlled the island anyway. Nonetheless, keeping with the spirit of the times, the US annexed Hawaii on July 7, 1898. Hawaiians were given full US citizenship. Because the US had such a massive business interest in Hawaii, and so many American businessmen lived there, this came as little surprise.
The US switch to imperialist behavior that occurred in 1898 has been a topic of great historical attention. After all, the US has generally claimed to stand in opposition to the practice of taking colonies, to be an advocate of freedom, democracy, and self-government for all. Some historians believe that this imperialist period was a "Great Aberration", a mistake that the US would never repeat, and one that goes against everything the US stands for. Others think that America really continued to have a kind of "informal colonial" influence throughout the twentieth century. By "informal colonialism", they mean that the US has promoted democracy as a means to opening foreign markets for Anerican manufactures and sources of raw materials. In this way, through a subtle dominance based on economics rather than direct politics, the US was able to create the same economic relationship that European powers had with their colonies. Under this view, the colony grabbing of 1898 (Guam, Hawaii, Philippines, Puerto Rico) was only the most obvious episode of American imperialism; it was the short period before the US discovered more subtle methods of economic domination, known as "neo-imperialism".
So how could Americans suddenly shift from anti-imperialism to jingoism? One explanation says that what really made the difference was a sudden shift in opinion among a "Foreign Policy Elite" consisting largely of businessmen, intellectuals, politicians, bureaucrats, and newspapermen. Partially, this shift might have occurred because of economic motivation, especially the search for new markets and the need to protect those markets with coaling stations, as advocated by Mahan. Alternatively, imperialism could have been a continuation of "Manifest Destiny", the ideology that fueled westward expansion. With the West mostly won, people now looked elsewhere to expand. The "Foreign Policy Elite" also may have justified imperial expansion using the theory of Social Darwinism, which suggested that only the strongest nations would survive, and that fierce competition was natural and necessary. Protestant ideals and a desire to educate and "Christianize" various groups was also an interest (even though the Filipinos had already been Catholic for centuries). Finally, the Foreign Policy Elite might have looked to Europe and followed the example set by European imperialists, in particular Great Britain. Most likely is that some mixture of these various factors all worked together to change the mind of the Foreign Policy Elite regarding the acquisition of an American empire.
The conquests of 1898 did not entirely mimic the European colonial model. In some senses, American actions 1898 represented a "New Imperialism", a new and unique empire, separate from the European colonial tradition and distinctly American. American imperialism was not a rejection of the anti-colonialism of the early republic, but a conscious choice based on economic motivations that held true before and after 1898. Americans were not merely aping the trappings of the European colonial experience. Instead of seeking empire for God, glory or gold, some would argue that American imperialism sought markets for industrial overproduction. Furthermore, access to foreign markets rather than actual political control of markets was the goal. In earlier mercantilist philosophies, nations sought colonies as outlets for their finished goods and as sources of raw materials for their extractive economies. American imperialists, though, wanted colonies that would serve to keep foreign markets accessible and open, not colonies that would be the markets themselves. The Philippines were important not only for a population of 7 million, but because the island provided room for a naval base from which the US could protect its business interests in Japan and China.