History Shorts: Constantinople sacked (1204)

In 1203, Western Europeans traveled to the Middle East to try and capture Jerusalem. They stopped at Constantinople along the way and decided to lay siege. Eastern and Western Christianity were at odds over doctrine and cultural differences. The Byzantines massacred Catholics a couple decades earlier adding incentive to the Crusader strike. They captured and sacked the city for plunder and revenge. The incident severely weakened the Byzantine Empire allowing the Muslims to gain a firmer foothold in the region. It is considered one the nails in the Byzantine coffin.
http://www.youtube.com/watch?v=XBx8BDJdzf