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: -Texas claimed the Rio Grande River as its southern boundary while Mexico claimed the Nueces River that was almost 100 miles further north as the boundary. The United States’ quick offer of annexation to Texas enraged the Mexican government and seemingly left them no choice but to follow through on their threats of war.

Detailed explanation-4: -Mexico, who refused to formally recognize Texas’ independence in the first place, pushed back against Texas’ desire to set their Republic’s border at the Río Grande. Mexico contested that Texas had to move the line back to the Nueces River, which runs through modern day Corpus Christi.