In the Mexican American War (1846-1848), the U.S. conquered the northern half of Mexico. In the Spanish-American War of 1898, the U.S. seized control of the Philippines, Guam, Puerto Rico, and Cuba. After these acts of imperialism, when one country extends its authority over another, the U.S. became a world power.

Why did American leaders think it was important to keep the Philippines? American leaders believed it was important to keep the Philippines because they believed Americans had a responsibility to govern the Filipinos, as they were an uncivilized people.

World War II transformed the United States from a midlevel global power to the leader of the “free world.” With this rapid rise in power and influence, the United States had to take on new responsibilities, signaling the beginning of the "American era."

Americans who advocated annexation evinced a variety of motivations: desire for commercial opportunities in Asia, concern that the Filipinos were incapable of self-rule, and fear that if the United States did not take control of the islands, another power (such as Germany or Japan) might do so.

More than principle and benevolence, it was actually white racist antagonism toward Filipino farm laborers in California, and the American agricultural entrepreneurs' fear of the “great menace” that Philippine products posed to them, that played a major role in the “grant” of independence to the Philippines.

For decades, the United States ruled over the Philippines because, along with Puerto Rico and Guam, it became a U.S. territory with the signing of the 1898 Treaty of Paris and the defeat of the Filipino forces fighting for independence during the 1899-1902 Philippine-American War.

Mahan urged govern- ment officials to build up American naval power in order to compete with other powerful nations. As a result of the urging of Mahan and others, the United States built nine steel-hulled cruisers between 1883 and 1890.