On this day (10 February, 1258) the Mongols destroyed Baghdad, killing between 200,000 and 1,000,000 people.

http://lostislamichistory.com/mongols/

Much more important was the military incompetency of the Abbasid Caliphate, the political disunity of Persia, Iraq, and Syria, and the momentum the Mongols had after conquering the Jin Dynasty. Blaming the conquest on the scholars is amateur and dishonest

Youtube video which may be useful: 

http://youtu.be/OA4foarxj_o