Which concept defined U.S. foreign policy in the late 19th and early 20th centuries regarding territorial expansion?

The concept of Manifest Destiny defined U.S. foreign policy in the late 19th and early 20th centuries regarding territorial expansion. This idea, prevalent from the 1840s onward, held that it was the United States' divine right and destiny to expand its territory across North America and beyond. Manifest Destiny was rooted in the belief that American democracy and culture were superior and that it was the nation's duty to spread these values.

During this period, the United States engaged in various forms of territorial expansion, including the annexation of Texas, the acquisition of Alaska, and the pursuit of interests in the Pacific and Caribbean. The notion of Manifest Destiny justified interventions and the expansion of U.S. influence, contributing to events such as the Spanish-American War, which further extended American territories overseas.

This belief system galvanized both public support for expansionist policies and the justification for the United States' interventions in foreign lands, aligning closely with the imperialistic tendencies that defined U.S. foreign affairs in that era.