Complex sentence: In 983, Bakjur quarrelled with Sa'd al-Dawla and went over to the Fatimids, who gave him troops with which he attacked Aleppo in September.
Split into simpler sentences: In 983, Bakjur quarrelled with Sa'd al-Dawla and went over to the Fatimids. The Fatimids supplied him with an army, with which he attacked Aleppo in September.