CLEO′MENES III., the 31st king of Sparta of the Agid line, was the son of Leonidas II. After the death of Agis IV., B. C. 240, Leonidas married his widow Agiatis to Cleomenes, who was under age, in order, as it seems, to bring into his family the inheritance of the Proclidae. Agiatis, though at first violently opposed to the match, conceived a great affection for her husband, and she used to explain to him the principles and designs of Agis, about which he was eager for information. Cleomenes was endowed, according to Plutarch, with a noble spirit; in moderation and simplicity of life he was not inferior to Agis, but superior to him in energy, and less scrupulous about the means by which his good designs might be accomplished. His mind was further stirred up to manliness and ambition by the instructions of the Stoic philosopher Sphaerus of Borysthenes, who visited Sparta. To this was added the influence of his mother Cratesicleia. It was not long, therefore, before Cleomenes had formed the design of restoring the ancient Spartan discipline, and the death of his father, whom he succeeded (B. C. 236), put him in a position to attempt his projected reform; but he saw that careful preparations must first be made, and that Sparta was not to be restored by the means which Agis had employed. Instead of repeating the vain attempt of Agis to form a popular party against the Ephors, the impossibility of which was proved by the refusal of Xenares, one of his most intimate friends, to aid his efforts, he perceived that the regeneration of Sparta must be achieved by restoring to her her old renown in war, and by raising her to the supremacy of Greece; and then that, the restored strength of the state being centred in him as its leader, he might safely attempt to crush the power of the Ephors. It was thus manifest that his policy must be war, his enemy the Achaean league. Lydiadas, the former tyrant of Megalopolis, foresaw the danger which the league might apprehend from Cleomenes; but the counsels of Aratus, who was blind to this danger, prevailed; and the proposal of Lydiadas, to make the first attack on Sparta, was rejected.