Complex sentence: While at Deraa on 21 September during his retreat from Nazareth to Damascus, Liman von Sanders ordered the Fourth Army to retreat without waiting for the II Corps/Southern Force, which also had begun to retreat north from Ma'an and the southern Hejaz railway.
Split into simpler sentences: While at Deraa on 21 September during his retreat from Nazareth to Damascus, Liman von Sanders ordered the Fourth Army to retreat. They were to move without waiting for the II Corps/Southern Force, which had also begun to retreat north from Ma'an and the southern Hejaz railway.