Annexation refers to the act of incorporating a territory or country into another political entity. Manifest Destiny is the belief that it was the destiny and duty of the United States to expand its territory across North America. These two terms are related in that annexation was often justified under the ideology of Manifest Destiny. This belief fueled the annexation of territories such as Texas, California, and Oregon, as well as the acquisition of land from Mexico through the Mexican-American War. Manifest Destiny provided the justification and motivation for the United States to expand its territory through annexation.
