The Aeacid Kingdom, alternatively referred to as the Kingdom of Epirus, was a major political force in Greece and southern Italy during the Classical Era before the Roman conquest. As one of the Diadochi, the Aeacid Kingdom tried, over several different leaders, to reunify the Empire of Alexander but ultimately failed in every attempt. King Pyrrhus was the most successful in this attempt, and at different points held Greece, southern Italy, and Egypt. The Kingdom ultimately fell during the Epirote War against Rome and its Greek allies of Argos and the Antigonids.
The realm that would become the Aeacid Kingdom was the core area of the Kingdom of Epirus. During Alexander's rise to power over all of Greece, the Kingdom folded before him rather than be destroyed by his armies. Already ruled by Alexander's distant cousins, they helped Alexander complete his campaigns in Italy and Sicily before returning to conquer the East. When he did, he placed his cousin Aeacides in command of the Western Greek cities.
Aeacides ultimately did not do a good job at his task of protecting the Western borders, as the Carthaginians and Samnites ate away at some of the more distant outposts. Instead, he focused on securing the safety of his relatives, Alexander's wife and children, hoping to bolster his claim amongst the Diadochi as Alexander's rightful successor. Before anything could be made of it, he died, to be succeeded by his underage son Pyrrhus and Aeacides' brother Alexander under a regency.
Pyrrhus ultimately came to the throne and married Alexander's daughter Helena to reinforce the same claim. Possessing a military mind considered second only to Alexander, he began his campaign of conquest to restore the Empire. He swiftly forced the Antigonids out of Macedonia and Greece, consolidating his claim in the center of the Hellenic world. He also removed his political rival and Alexander's son, Alexander IV, by conquering Egypt and installing him as puppet. Before he could continue any conquests further east, the situation in Italy had demanded his attention.Under increasing threat from the Romans and Carthaginian occupation, the Greek cities of southern Italy demanded that Pyrrhus turn his attentions west and put an end to the threats that they faced. Backed into a corner, Pyrrhus complied and sailed to Italy with a powerful army while Rome and Carthage, fearful of Pyrrhus' reputation, allied against him. In the ensuring Pyrrhic War, Pyrrhus managed to liberate Sicily and southern Italy for a time before being forced to withdraw after suffering huge casualties. Unable to beat the larger supply of manpower, Pyrrhus abandoned the Italian cities and returned to Greece.