In the Fourth Crusade Norman crusaders, attempting to form a Latin Empire, sacked Constantinople, almost completely destroying the city. They burned the Imperial Library of Constantinople, which preserved much of the knowledge of the ancient world.
The 1204 sack of Constantinople has been described as one of the most profitable and disgraceful sacks of a city in history. What the Crusaders did not plunder they burned. It is estimated that more destruction was done to the city and its libraries during this sack than occurred during the seige of Constantinople by the Turks in 1453. It is also believed that crusaders may have sold some Byzantine manuscripts to Italian buyers.