Complex sentence: The next day, on 19 September, Serb units from other parts of the front line forced the Croat army to retreat back over the river, with Serb planes from the Banja Luka airport attacked in the vicinity of village Živaja and Šaš in Croatia.
Split into simpler sentences: The next day, on 19 September, Serb units from other parts of the front line came and forced the Croat army back over the river. That day Serb planes from the Banja Luka airport attacked the Croatian army in vicinity of village Živaja and Šaš in Croatia.