Question

What was Polk’s argument for declaring war against Mexico?

Mexico had attacked American troops on American soil.

Mexico had interfered with negotiations for Oregon.

Mexico had kidnapped American missionaries in western territory.

Mexico had urged Native Americans to attack American settlers.

Answer 1

Mexico had attacked American troops on American soil.

Polk cited the Thornton Affair—Mexican forces firing on U.S. troops in the disputed area between the Nueces and the Rio Grande—and told Congress that "Mexico has shed American blood upon American soil," requesting a declaration of war.