The document summarizes the expansion of Greece through key conflicts with Persia and internally between Athens and Sparta. It describes how the Persians twice tried to conquer Greece but were defeated at Marathon and Salamis. It then discusses the rise of Athens' power through the Delian League and leadership of Pericles, before tensions grew into the 27-year Peloponnesian War between Athens and Sparta's rival Peloponnesian League, culminating in Athens' surrender in 404 BC.