The Battle of Sellasia was fought in 222 BC between the Achaean League (supported by the Macedonians) and Sparta under the command of King Cleomenes III.
Before this war, the Achaean League had successfully fought the Macedonians and reduced their influence in the Peloponnese. However, the growth of the Achaean League was not to the liking of Sparta, who, moreover, managed to drag many of the cities of the League over to their side, as the cities in question feared total destruction.
The growth of Sparta's power did not escape the attention of the Achaeans, who had to go to war with Sparta. They enlisted the help of the Macedonian king Antigonus III. Doson, their recent enemy.
At the Battle of Sellasia, the Achaean alliance won, but in the process restored Macedonian hegemony in the Peloponnese. The Spartan king Cleomenes III subsequently fled to Alexandria, Egypt.