The Spanish forces of Hernan Cortes start their march on Tenochtitlán in December 1520. The capture of the city iin August 1521 marks the fall of the Aztec empire.
Editors. "Aztec capital captured by the Spanish and their allies". The Literary Encyclopedia. First published 01 March 2010
[http://www.litencyc.com/php/stopics.php?rec=true&UID=9945, accessed 20 December 2014.]