Where the blame lies for the Mexican-American War is hard to define. The westward movement of Americans in response to manifest destiny has been established as the ultimate cause of the war. Certain parts of North America were simply "destined" to become part of the United States. However, it is important to examine surrounding issues and other possible causes. .
Many believe that President Polk, with his aggressive promises and desire to gain California at all costs, was the main cause of the Mexican-American War. However, looking back to the previous term, signs of war can be seen with President Tyler as well. Tyler, being unpopular with both the Democrat and Whig parties, believed that by connecting his name to American expansion he could gain respect. He ran for a second term hoping to realize his dream, but Polk won the election instead. In one last attempt, Tyler sent messengers to Texas on the last day of his term calling for the immediate occupation of Texas, upsetting the Mexicans. Although Polk could have easily called back the messengers to avoid conflicts, he did nothing and Mexico declared it an act of war.
Although Polk's actions had a significant impact on the outcome of this specific conflict, some blame can also be placed on the people. The settling of Texas and other western areas played a major role in the war between America and Mexico. By moving ahead of official inhabitation and settling early on land west of America's boundaries, these Americans were hoping to sell the land at high prices to farmers, plantation owners, and the like. Settlers assumed that their lands would eventually become part of the United States. .
Still others, including many people in the United States, placed the majority of the blame for the Mexican-American War on Mexico. Believing the boundary was the Rio Grande, President Polk sent troops under General Zachary Taylor to the region between the Rio Grande and Nueces Rivers, at which point Mexican forces attacked.