The Peloponnesian War caused turmoil in Greece as Athens and Sparta, the two main powers, engaged in a massive bloody conflict over control of the Aegean Sea. During the war, Socrates emerged as an important philosopher while Athens' leader Pericles built protective walls. Eventually, Athens' forces were defeated by Sparta's General Lysander at the Battle of Notium. After the war, Greece fell under the rule of tyrants although oral traditions and democracy were later restored.