Complex sentence: Ashwatthama went to torch the camping tents of the Pandavas at night, but he got confused with the Upapandavas (sons of Draupadi and pandavas) as they looked very similar to their fathers.
Split into simpler sentences: Ashwatthama went to torch the camping tents of the Pandavas at night. But he got confused with the Upapandavas (sons of Draupadi and pandavas) as they looked very similar to their fathers.