There were various actions that occurred in order to begin the Mexican-American war. But the final action that sparked the war was when the US government send general Taylor to a territory (Rio Grande) in order to reach to a treaty between the two countries but the Mexican general Pedro de Ampudia demanded for them to return and when that didn’t happen Ampudia killed and captured various American soldiers. When word got to Washington the president declared war and they officially started fighting over who will win the disputed territory.
