Treaty of Guadalupe Hidalgo - Conduct of War

Conduct of War

California and New Mexico were quickly occupied by American forces in the summer of 1846, and fighting there ended by January 1847 with the signing of the Treaty of Cahuenga and end of the Taos Revolt. The U.S. spent 1847 invading central Mexico and occupying Mexico City, but Mexico was still reluctant to agree to the loss of California and New Mexico, offering only sale of Alta California north of the 37th parallel north (north of Santa Cruz, California and Madera, California and the southern boundaries of today's Utah and Colorado) which was already dominated by Anglo-American settlers. Some Eastern Democrats called for total annexation of Mexico and claimed that some Mexican liberals would welcome this, but Pres. Polk's State of the Union address in December 1847 upheld Mexican independence and argued at length that occupation and any further military operations in Mexico were aimed at securing a treaty ceding California and New Mexico up to approximately the 32nd parallel north and possibly Baja California and transit rights across the Isthmus of Tehuantepec.

Jefferson Davis advised Polk that if Mexico appointed commissioners to come to the U.S., the government that appointed them would probably be overthrown before they completed their mission, and they would likely be shot as traitors on their return; so that the only hope of peace was to have a U.S representative in Mexico. Nicholas Trist, chief clerk of the State Department under Pres. Polk, finally negotiated a treaty with the Mexican delegation after ignoring his recall by Pres. Polk in frustration with failure to secure a treaty. Notwithstanding that the treaty had been negotiated against his instructions, given its achievement of the major American aim, President Polk passed it on to the Senate.