By the 1830s, the United States had begun the path toward its manifest destiny. However, to complete this vision of American expansion from the Atlantic to the Pacific, the nation had to acquire territory that was not yet in its possession. After numerous diplomatic offers presented to Mexico by President James Polk to acquire lands west of Texas, combined with a dispute over the geographic border between Texas and Mexico that ended with an ambush of American soldiers stationed at the Rio Grande, a war loomed between the United States and Mexico. When Texas was annexed into the United States in 1845, the U.S. government recognized the Rio Grande as the southern border of Texas.