Complex sentence: Hippias had fled to Persia, and the Persians threatened to attack Athens if they did not accept Hippias; nevertheless the Athenians preferred to remain democratic despite the danger from Persia.
Split into simpler sentences: Hippias had fled to Persia, and the Persians threatened to attack Athens if they did not accept Hippias back. Nevertheless, the Athenians preferred to remain democratic despite the danger from Persia.