External non-Islamic forces looted mosques and destroyed books. European scholars and book-dealers purchased or stole Islamic books for their own purposes. There was carelessness, neglect, and ignorance among the Muslims themselves. Internal disputes and civil and sectarian unrest took their toll.
Some collections became infested with worms and vermin. Some were destroyed by dirt, dust, and moths. Such natural disasters as flood, earthquake, and fire destroyed more.
(This page was updated in December 2012.)