alternatehistory.com

In 1842, the captain of the U.S. Pacific Squadron heard incorrectly that the U.S. was at war with Mexico and actually captured a city in Alta California called Monterey.

http://en.wikipedia.org/wiki/Capture_of_Monterey

What if this action created the war he thought already existed? :p

Would a Mexican-American War that occurs 4 years earlier change anything?
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