Dunbar-Ortiz explores the events leading up to the United States’ invasion of Mexico and its further expansion southwest and west in the mid-1800s. Reflecting the continuing development of the U.S. origin myth, racism underlying support for U.S. expansion was prevalent based on the ideas of Anglo-Americans as a superior race. The belief in manifest destiny drove the narrative of the United States expanding west to what it is today and justified invasions of Mexico and more Indigenous nations. Although historians have labeled the U.S. war against Mexico beginning in 1846 as its first foreign war, Dunbar-Ortiz rejects this, given the reality that the United States invaded numerous Indigenous nations already as well as the Berber Nation of North Africa in early 19th century. 

The 19th century also saw many struggles for independence against European colonial rule, such as in Haiti or in South America. The Republic of Mexico gained independence after a war against Spanish colonialism that left the new nation severely weakened yet pressed to defend itself from the United States’ encroachment. The United States’ efforts to annex areas formerly under Spanish rule began as early as 1806 with Jefferson’s military project called the Pike expedition.