Congress believed that a Mexican shot an American on American territory. The Mexicans believed that this was their territory. For that reason, Polk told the Congress, "cup of forbearance has been exhausted, even before Mexico passed the boundary of the United States, invaded our territory, and shed American blood upon American soil." Consequently, two days later Congress declared war on Mexico.
The Battle of the Alamo was in between the Texans and Mexico. In addition, the Battle was held at a fort in San Antonio. In fact, the Texans called it the Alamo. Lastly, Mexico won the battle. Unfortunately, all the American Soldiers died, but a war cry was created. "Remeber the Alamo."