Athenian failure to regain control of Boeotia at Delium and Brasidas' successes in northern Greece

The first phase of the war saw a series of fruitless annual invasions of Attica by Sparta, while Athens successfully fought the Corinthian empire in northwest Greece and defended its own empire, despite a plague that killed the leading Athenian statesman Pericles. The war turned after Athenian victories led by Cleon at Pylos and Sphakteria, and Sparta sued for peace, but the Athenians rejected the proposal. The Athenian failure to regain control of Boeotia at Delium and Brasidas' successes in northern Greece in 424 BC improved Sparta's position after Sphakteria.