In: Economics
In 1836 Texas became independent of Mexico. The United States initially declined to incorporate it into the Union, largely because northern political interests opposed the addition of a new slave state. The Mexican government has also encouraged border raids and warned that any attempt to annex would result in war.
Nonetheless, annexation proceedings were soon initiated after Polk 's victory in 1844, advocating for Texas to be "re-annexed" and for the Oregon Territories to be "re-occupied." Polk also had his sights on California, New Mexico, and the rest of what is now the United States. Southeast. When his bid to buy those lands was refused, he instigated a war by sending troops into a contested region between the Rio Grande and Nueces River that had traditionally been recognised by both countries as part of the Coahuila state of Mexico.
A declaration of war on May 13 was overwhelmingly approved by Congress, but the United States entered the war divided. Democrats, particularly those in the Southwest, have strongly favored the conflict. Most Whigs found Polk 's intentions to be cautious land grabbing. Indeed, Whigs challenged the veracity of Polk 's assertion that the initial conflict between U.S. and Mexican forces had taken place in U.S. territory from the outset, both in the Senate and the House. Additionally, legislators were at odds about whether Polk had the right to declare unilaterally that there was a state of war.
The biggest problem was where the incident really took place and Americans' reluctance to accept the Mexican assertion that the Nueces River formed the boundary between the two countries. Strong Whig resistance persisted deep into the conflict, not only to the validity of Polk 's claim but also to the war itself. In December 1846 Polk was accused of treason by his Whig doubters. The by-then Whig-controlled House voted 85 to 81 in January 1847 to censure Polk for having initiated war with Mexico "unnecessarily and unconstitutionally"