Excerpts from Books and Wikipedia
"The younger brother of the Emperor of Austria, the well-meaning Archduke Maximilian, arrived in Mexico with his young wife Carlotta, in 1864 to be crowned emperor. Quite wrongly, he believed that he had been accepted by what he henceforth regarded as 'his people.' In reality, he had been infiltrated into the country with the support of a French army, in furtherance of French imperialist ambitions, and in cahoots with rich Mexican land owners and the Roman Catholic Church. They wanted the new emperor to get rid of President Benito Juarez, who was threatening their wealth and power. . . . The French army, however, almost drove Juarez across the US border into Texas before the US government demanded their withdrawal under the Monroe Doctrine. In 1866, Napoleon III of France announced that his troops would be withdrawn. . . . The French left the following year. Maximilian would not abdicate and run, though, because he thought such action dishonorable. . . . Juarez returned to Mexico City the following month, and Mexico returned to being a republic." [Furtado: 1001 Days]