Battle of Sellasia

In 222 BC, King Cleomenes III of Sparta was defeated at Sellasia, a pass north of Sparta in Laconia, by an army of Macedonians and the Achaean League led by Antigonus III Doson of Macedon. Cleomenes' reforms had revived Spartan power, and his victories over the Achaean League had forced its leader Aratus to make the remarkable decision of asking Macedon, the League's old enemy, for help. In return, Antigonus received the fortress of Acrocorinth. Cleomenes fortified the pass at Sellasia with around 20,000 men, facing an allied army of about 29,000. The battle was hard fought. The Macedonian phalanx eventually broke the Spartan line, and most of Cleomenes' citizen soldiers were killed. Cleomenes fled to Egypt, where he later died after a failed uprising in Alexandria. Antigonus then entered Sparta, the first time in its history that the city was captured by a foreign army. He restored the old constitution and undid many of Cleomenes' reforms. The battle ended Sparta's last serious attempt to become a great power again.