Final answer:
The action of American soldiers moving into the region between the Nueces River and the Rio Grande contributed to the outbreak of conflict between the United States and Mexico. This led to the Mexican-American War and the eventual acquisition of Mexican territory by the United States.
Step-by-step explanation:
The action of American soldiers moving into the region between the Nueces River and the Rio Grande, a land claimed by both the United States and Mexico, contributed to the outbreak of conflict between the two countries. The United States had long argued that the Rio Grande was the border between the two nations, while Mexico claimed the Nueces River as the border.
The historical context of this action includes the annexation of Texas by the United States in 1845, which caused tensions between the two countries. The United States sought to expand its territory and establish the Rio Grande as the border, thus claiming more land outside of Texas.
The consequences of this action were significant. It led to the Mexican-American War, fought from 1846 to 1848. Mexico saw the American soldiers' presence as an invasion of their territory, and the conflict escalated from there. The war ultimately resulted in the United States gaining a substantial amount of Mexican territory.