Cleomenes III in the context of "Kings of Sparta"

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.

The Battle of Sellasia took place during the summer of 222 BC between Macedon and the Achaean League, led by Antigonus III Doson, and Sparta under the command of King Cleomenes III. The battle was fought at Sellasia on the northern frontier of Laconia and ended in a Macedonian-Achaean victory.

In 229 BC, Cleomenes initiated hostilities against the Achaean League, the dominant power of the Peloponnese. In a series of campaigns, Cleomenes was successful in defeating the Achaeans, making Sparta the main regional power. This prompted the chief figure of the Achaean League, Aratus of Sicyon, to approach the King of Macedon, Antigonus III Doson, for military assistance. The Macedonians acquiesced on the terms that the Achaean surrender the formidable fortress of Acrocorinth to them. The Macedonians invaded the Peloponnese in 224 BC at the head of a Greek alliance and by 222 BC managed to hem Cleomenes in Laconia.

The Battle of Mount Lycaeum was fought between Sparta led by Cleomenes III and the Achaean League commanded by Aratus. It was the first major battle of the Cleomenean War. The battle occurred at Mount Lycaeum on the border of Elis and Arcadia and ended in a Spartan victory.

Agesipolis III (Ancient Greek: Ἀγησίπολις; died 183 BC) was the 32nd and last of the kings of the Agiad dynasty in ancient Sparta.

Agesipolis was the son of another Agesipolis and grandson of Cleombrotus II and Chilonis, daughter of Leonidas II and Cratesiclea. After the death of Cleomenes III he was elected king while still a minor, and placed under the dubious guardianship of an uncle named Cleomenes. Agesipolis was, however, soon deposed by his colleague Lycurgus. In 195 BC, he was at the head of the Lacedaemonian exiles, who joined Titus Quinctius Flamininus in his attack upon Nabis, the tyrant of Lacedaemon (see War against Nabis). Agesipolis was a member of an embassy sent about 183 to Rome by the Lacedaemonian exiles, and, with his companions, was intercepted by pirates and killed.

Cleombrotus II (Greek: Κλεόμβροτος Β΄) was a Spartan king of the Agiad dynasty. He married into the royal family via the daughter of Leonidas II, Chilonis. Chilonis's mother was a Persian/Seleucid woman, and Cleombrotus II's wife was therefore not fully Spartan. This created friction between Cleombrotus II's father-in-law and then co-regent Agis IV when it came to succession. Cleombrotus II nevertheless succeeded Leonidas II when the latter fled to avoid trial after clashing with co-regent's reforms, and reigned from 242 BC to 241 BC before Leonidas II returned and once more took the throne. He then sent Cleombrotus II and Chilonis into exile. Cleomenes III, Leonidas II's son, eventually succeeded his father at his death.