All of Mexico Movement

Both approaches failed, and it was only due to this increase in violence and insurrection that Mexican leaders saw the necessity of establishing a peace with the US.

Idealistic advocates of Manifest Destiny, such as John L. O'Sullivan, had always maintained that the laws of the United States should not be imposed onto people against their will.

The annexation of all of Mexico would violate that principle and find controversy by extending US citizenship to millions of Mexicans.

Identitarian ideas inherent in Manifest Destiny suggested that Mexicans, as people of color, would present a threat to white racial integrity and so were not qualified to become US citizens, but the "mission" component of Manifest Destiny suggested that Mexicans would be improved (or "regenerated," as it was then described) by bringing them into American democracy.

An example of this identity-based and racist position was that of John C. Calhoun, Senator from South Carolina, former vice president and future spokesperson for southern secession, in which, in his own words in a speech to Congress on January 4, 1848, he explained that: [We] have never dreamt of incorporating into our Union any but the Caucasian race the free white race.

[3][4] The controversy was eventually ended by the Mexican Cession, which added the territories of Alta California and Nuevo México to the United States, both more sparsely populated than the rest of Mexico.