Complex sentence: Shirkuh was sent back into Egypt in 1167, with Shawar once again allying with Amalric, who besieged Shirkuh in Alexandria until he agreed to leave; however, a Crusader garrison remained in Egypt and Amalric allied with the Byzantine Empire, planning to conquer it entirely.
Split into simpler sentences: Shirkuh was sent back into Egypt in 1167, with Shawar once again allying with Amalric. Amalric besieged him in Alexandria until he agreed to leave; a Crusader garrison, however, remained in Egypt and Amalric allied with the Byzantine Empire, planning to conquer it entirely.