The rebellion of Texas and its corresponding entrance into the United States set off a clash with Mexico. The problem with Texas joining the United States from the U.S. point of view was adding yet another slave territory, but for Mexico it was the contention over Texas' independence from Mexico in the first place. President Polk, an avid expansionist, moved troops in the disputed border regions and as Mexico did as well, border clashes resulted in a war which would see propaganda from pro-war advocates and anti-war advocates and show the cracks in the union which would result in Civil war in another 14 years from the start of the Mexican–American War.