Aratus sent an embassy to Antigonus III in 226BC seeking an unexpected alliance now that the reformist king Cleomenes III of Sparta was threatening the rest of Greece in the Cleomenean War (229–222BC). In exchange for military aid, AntigonusIII demanded the return of Corinth to Macedonian control, which Aratus finally agreed to in 225BC. In 224BC, AntigonusIII's forces took Arcadia from Sparta. After forming a Hellenic league in the same vein as PhilipII's League of Corinth, he managed to defeat Sparta at the Battle of Sellasia in 222BC. Sparta was occupied by a foreign power for the first time in its history, restoring Macedonia's position as the leading power in Greece. Antigonus died a year later, perhaps from tuberculosis, leaving behind a strong Hellenistic kingdom for his successor PhilipV.