Cleomenean War

The Cleomenean War (229/228–222 BC) was fought between Sparta and the Achaean League for the control of the Peloponnese. Under the leadership of king Cleomenes III, Sparta initially had the upper hand, which forced the Achaean League to call for help the Macedonian king Antigonos Doson, who decisively defeated Cleomenes in the battle of Sellasia in 222.

In 235 BC, Cleomenes III (r. 235–222 BC) ascended the throne of Sparta and began a program of reform aimed at restoring traditional Spartan discipline while weakening the influence of the ephors, elected officials who, though sworn to uphold the rule of Sparta's kings, had by the time of Cleomenes come to wield extraordinary political power in the Spartan system. When, in 229 BC, the ephors sent Cleomenes to seize a town on the border with Megalopolis, the Achaeans declared war. Cleomenes responded by ravaging Achaea. At Mount Lycaeum he defeated an army under Aratus of Sicyon, the strategos of the Achaean League, that had been sent to attack Elis, and then routed a second army near Megalopolis.

In quick succession, Cleomenes cleared the cities of Arcadia of their Achaean garrisons, before crushing another Achaean force at Dyme. Facing Spartan domination, Aratus was forced to turn to Antigonus III Doson (r. 229–221 BC) of Macedon. In return for Macedonian assistance, the Achaeans were obliged to surrender the citadel overlooking Corinth to Antigonus. Cleomenes eventually invaded Achaea, seizing control of Corinth and Argos, but was forced to retreat to Laconia when Antigonus arrived in the Peloponnese. Cleomenes fought the Achaeans and the Macedonians at Sellasia, where the Spartans were routed. He then fled to the court of his ally, Ptolemy III of Egypt (r. 246–222 BC), where he ultimately committed suicide in the wake of a failed revolt against the new Pharaoh, Ptolemy IV (r. 221–205 BC).

Cleomenes III ascended the throne of Sparta in 236 BC or 235 BC, after deposing his father, Leonidas II. His accession to power ended a decade-long period of heightened conflict between the two royal families. Sparta's ancient dual kingship was explained by the founding legend that the original conquerors of Sparta were twin brothers and their descendants shared Sparta. During the turmoil, Leonidas II had executed his rival king, the reformist Agis IV.

In 229 BC, Cleomenes took the important cities Tegea, Mantineia, Caphyae, and Orchomenus in Arcadia, who had by then allied themselves with the Aetolian League, a powerful Greek confederation of city states in central Greece. Historians Polybius and Sir William Smith claim that Cleomenes seized the cities by treachery; however, Richard Talbert, who translated Plutarch's account of Sparta, and historian N. G. L. Hammond say Cleomenes occupied them at their own request. Later that year, the ephors sent Cleomenes to seize the Athenaeum, near Belbina. Belbina was one of the entrance points into Laconia and was disputed at the time between Sparta and Megalopolis. Meanwhile, the Achaean League summoned a meeting of her assembly and declared war against Sparta. Cleomenes in return fortified his position.

Aratus of Sicyon, the strategos of the Achaean League, tried to re-take Tegea and Orchomenus in a night attack. Efforts from inside the city failed, though, and Aratus quietly retreated, hoping to remain unnoticed. Cleomenes nonetheless discovered the plan and sent a message to Aratus asking about the goal of his expedition. Aratus replied that he had come to stop Cleomenes from fortifying Belbina. Cleomenes responded to this by saying: "If it's all the same to you, write and tell me why you brought along those torches and ladders."

After fortifying Belbina, Cleomenes advanced into Arcadia with 3,000 infantry and a few cavalry. However, he was called back by the ephors, and this retreat allowed Aratus to seize Caphyae as soon as Cleomenes returned to Laconia. Once this news reached Sparta, the ephors sent Cleomenes out again; he managed to capture the Megalopian city Methydrium before ravaging the territory surrounding Argos.

Around this time, the Achaean League sent an army under a new strategos—Aristomachos of Argos, who had been elected in May 228 BC—to meet Cleomenes in battle. The Achaean army of 20,000 infantry and 1,000 cavalry advanced on the 5,000-strong Spartan army at Pallantium. Aratus, who had accompanied Aristomachos, advised him to retreat because even 20,000 Achaeans were no match for 5,000 Spartans. Aristomachos, listening to Aratus' advice, retreated with the Achaean army.