In the Texas territory in the early 1840’s, the Americans revolted under Mexico’s rule. Even though they promised to follow Mexico’s rules, they did not want to keep those promises, and issues like slavery and religion became key problems with the Mexicans and the Americans.
In 1845, President Tyler Annexed Texas. He saw that there was a large amount of support for the New Democratic candidate James Polk, and he passed the annexation, even though Mexico never actually relinquished control of Texas.
When James Polk got elected, he sent General Zachary Taylor along with 4000 men to march from the Nueces River to the Rio Grande