The AEtolians, dissatisfied with these arrangements, persuaded Antiochus III., king of Syria, to enter into a league against the Romans. He passed over into Greece with a wholly inadequate force, and was defeated by the Romans at Thermopylae (B.C. 191). The AEtolians were now compelled to make head against the Romans by themselves. After some ineffectual attempts at resistance they were reduced to sue for peace, which they at length obtained, but on the most humiliating conditions (B.C. 189). They were required to acknowledge the supremacy of Rome, to renounce all the conquests they had recently made, to pay an indemnity of 500 talents and to engage in future to aid the Romans in their wars. The power of the AEtolian league was thus for ever crushed, though it seems to have existed, in name at least, till a much later period. The Achaean league still subsisted but was destined before long to experience the same fate as its rival. At first, indeed, it enjoyed the protection of the Romans, and even acquired an extension of members through their influence, but this protectorate involved a state of almost absolute dependence. Philopoemen also had succeeded, in the year 192, in adding Sparta to the league, which now embraced the whole of Peloponnesus. But Sparta having displayed symptoms of insubordination, Philopoemen marched against it in 188, and captured the city; when he put to death eighty of the leading men, razed the walls and fortifications, abolished the institutions of Lycurgus, and compelled the citizens to adopt the democratic constitution of the Achaeans. Meanwhile the Romans regarded with satisfaction the internal dissensions of Greece, which they foresaw would only render her an easier prey, and neglected to answer the appeals of the Spartans for protection. In 183 the Messenians, under the leadership of Dinocrates, having revolted from the league, Philopoemen, who had now attained the age of 70, led an expedition against them; but having fallen from his horse in a skirmish of cavalry, he was captured, and conveyed with many circumstances of ignominy to Messene, where, after a sort of mock trial, he was executed. His fate was avenged by Lycortas, the commander of the Achaean cavalry, the father of the historian Polybius.