Born Ferdinand Maximilian Joseph of the House of Hapsburg-Lorraine, Maximilian was installed as the Emperor of Mexico after the Franco-Mexican war, with the backing of Napoleon III and conservatives within the Mexican government.
Maximilian was met with ferocious attacks by republican rebels upon taking the throne, but managed to put down the revolutionaries as they lacked resources, leading to the execution or emigration to the United States and CSA of the beaten rebels.
Against what the conservative monarchists thought the Emperor would bring, Maximilian was fairly liberal, and enacted such policies as land reforms, religious freedoms, and extending the right to vote beyond the landholding class. Maximillian also modernized and industrialized his nation, enacted military reform and built up the Mexican navy; all of which would aid Mexico irrevocably in the war with the Confederacy.
Maximilian died on July 19, 1902 at the age of 70 and was succeeded by his son, Michael I.
Since the Imperial house began, Mexico has been shaky in alliances, earlier making friendships with the CSA which dissolved as their imperialist eye toward the Mexican lands became apparent, and later with the US. Friendships with the two nations have flip flopped sporadically since.