 Polk deployed a military detachment led by General Zachary Taylor to back up his assertion that the Rio Grande constituted the Southern border of both Texas and the United States.After Taylor's forces clashed with Mexican soldiers north of the Rio Grande, Polk asked for a declaration of war in early 1846, asserting that Mexico had invaded American territory.Though some Whigs questioned whether Mexico had started an aggressive war, both houses of Congress declared war, with the House voting 174-to-14 to approve the declaration.