French forces under General E.F. Forey had taken Mexico City the month before and soon after appointed a Junta Superior de Gobeirno . On July 8, the Assembly of the Junta met and two days later issued the proclamation that Mexico was now an hereditary empire. The throne was offered to Archduke Maximillian of Austria but, failing that, the document stated that "the Mexican people relies on the good will of His Majesty Napoleon III, Emperor of the French, to indicate for it another Catholic Prince." Maximillian accepted in October 1863. (By John Osborne)
Source Citation
John Musser, The Establishment of Maximilian's Empire in Mexico (Manasha, WA: The Collegiate Press, 1918) 60-61.