The last Abbasid caliph. Mustasim reigned from 1242 to 1258. Halaku the grandson of Genghis Khan invaded Baghdad in 1258. The Caliph was powerless and surrendered along with his 300 officials: ten days later they were all put to death. Halaku burned and plundered the city and Islam was left without a Caliph for the first time since its inception.