Complex sentence: At the Battle of Coronea (394 BC), Spartan forces under Agesilaus II defeated the Thebans during the Corinthian War, avenging the Spartan defeat at Haliartus, where Lysander had been killed.
Split into simpler sentences: At the Battle of Coronea (394 BC), Spartan forces under Agesilaus II defeated the Thebans. This encounter took place during the Corinthian War, and it avenged the Spartan defeat at Haliartus, where Lysander had been killed.