But what should have been their triumph proved to be their destruction. For the frustration of their hopes Polybius,[134] who voices the opinion of Aratus, held the Ætolians responsible, and it is likely that he was in the main right. For just at this critical moment, when the Achæans were face to face with the most serious problem which their federal system presented, namely, the reluctance of states, like Sparta and Athens, which were markedly stronger than the common run of the Achæan cities, to accept mere equality with them, the Ætolians not only left them in the lurch and made an advantageous peace for themselves with Antigonus Doson, the new king of Macedon, but, by ceding to Sparta their Arcadian cities (Tegea, Mantinea, Orchomenus, and Caphiæ), they made it possible for Cleomenes, the young Spartan monarch, to rally round himself all the Peloponnesian opposition to the Achæans, and to make a brilliant effort to establish once again the Spartan hegemony in the peninsula. Another view of the matter is that the downfall of the Achæan league--which, to escape Cleomenes, threw itself into the arms of Antigonus Doson--was due to the intervention of Ptolemy III, who backed up Sparta, Athens, and Ætolia by his friendship and his money,[135] and would have gladly seen Achæa eliminated in order that Greece might present a united front to Antigonus Doson. In any case it was Antigonus Doson who reaped the benefits, and it seems unlikely that they were wholly an unearned increment. What he was capable of he had already shown by joining heartily in the international guarantee of the neutrality of Athens which had robbed Aratus of that choice prize. He was clearly no common man, and had he not died an untimely death shortly after the great victory he gained over Cleomenes at Sellasia (222 B.C.), he would probably have been much better known in history. His energetic and tactful conduct in this crisis contrasts sharply with the nerveless backdown of Egypt, for which the only excuse was the imminent demise of Euergetes and the threatening attitude of Antiochus the Great. It cannot be denied that Antigonus Doson made a good use of all his opportunities.