Question

What reason did president James K Polk give when he asked Congress to declare war against Mexico ?

Answer 1

Reference to the Rio Grande boundary of Texas was omitted from the U.S. Congress's annexation resolution to help secure passage after the annexation treaty failed in the Senate. President Polk claimed the Rio Grande boundary, and when Mexico sent forces over the Rio Grande, this provoked a dispute.

I was here 1st

Answer 2

To stop Mexican attacks against U.S. territory