So late one night, the traitor led the Spartans into his own city. The Spartan army captured Athens and took over. Sparta became the strongest city in Greece. But most of the Athenian men and many of the Spartan soldiers had died in the long, long Peloponnesian War. Now Greece no longer had the men they needed to keep other invaders away. The Greeks had spent all their energy fighting each other; they had none left to defend themselves.
