Fifteen years before the United States was plunged into Civil War, it fought a war against Mexico that added half a million square miles of territory to the United States. Not only was it the first American war fought almost entirely outside the United States, it was also the first American war to be reported, while it happened, by daily newspapers.
The most dramatic event in the history of relations between Mexico and the United States took place a century and a half ago. U.S. historians refer to this event as "The Mexican War," while in Mexico we prefer to use the term "The U.S. Invasion."
When asked about the Mexican American War; most Americans would probably give a lost and questioning reaction. However for Mexicans, they would probably remember this war passionately; “It is a scar for them"
the Americas thought the had the rig to control and spread across the continents to the pacific ocean.