Complex sentence: The Athenians were forced to give up control of Boeotia, and the defeat led to revolts on Euboea and in Megara, which in turn led to further conflict with Sparta, contributing to the Peloponnesian War.
Split into simpler sentences: The Athenians were forced to give up control of Boeotia. The defeat led to revolts on Euboea and in Megara, which in turn led to further conflict with Sparta, contributing to the Peloponnesian War.