Texas was originally Mexican so therefore it gained its independence from Mexico. America first refused to add it to it’s union since this was the period where the North wanted to stop slavery since they did not require them. Polk, sent a request stating that Texas should be “re-annexed” or re added as well as having people “re-occupy” Oregon. The 2 countries went to war and since Mexico’s military was weak and unprepared, Mexico lost nearly half of its territory. Having the Guadaloupe treaty, helped a lot to end the war.