During our Civil War, Napoleon III sent an army to conquer Mexico, so he could support the Confederacy and end the threat of the United States of America.  At the Battle of Pueblo, on the Fifth of May of 1862, 4,000 Mexicans stopped an 8,000 man French army in their tracks.  That bought the Union the time it needed to defeat the Confederacy at Gettysburg.  That time kept our nation together.  It started on Cinco de Mayo.