USA HISTORY

Detailed explanation-1: -It stemmed from the annexation of the Republic of Texas by the U.S. in 1845 and from a dispute over whether Texas ended at the Nueces River (the Mexican claim) or the Rio Grande (the U.S. claim).

Detailed explanation-2: -The immediate cause of the Mexican-American War was a disputed boundary between the United States and Texas on the Nueces Strip. Mexico did not recognize Texas as legitimate American territory and Texas admission to the United States antagonized Mexican officials and citizens.

Detailed explanation-3: -He sent an American diplomat, John Slidell, to Mexico City to offer $30 million for it. But the Mexican government refused to even meet with Slidell. Polk grew frustrated. Determined to acquire the land, he sent American troops to Texas in January of 1846 to provoke the Mexicans into war.