This study explores diplomatic manoeuvres of the Hellenistic states in the First Macedonian War (c. 214-205 BCE), and, in particular, during the period from the alliance between Rome and Aitolia (211) to the Peace of Phoinike (205). Scholars have tended to argue that the Romans in the middle of the Second Punic War (218-201) succeeded in managing this conflict with Philippos V of Macedonia Certainly, Rome prevented this king, an ally of Carthage, from participating in the desperate struggle against the Carthaginians in Italy. However, in 206/5 the Romans were deserted by the Aitolians, their ally, and as a result of the peace in 205, lost a part of their sphere of influence in Illyria although the republic was not defeated militarily. This was partly brought about by the fact that Rome wanted to concentrate on the conquest of Carthage, and felt it necessary to make some concession to Macedonia for a cessation of hostilities in the East. But Philippos also had to manage many enemies simultaneously. The peace cannot be considered the result of the successful tactics of the Romans but that of their failure in intemational politics. The validity of this theory is shown by the analysis of three factors: the diplomacy of Greek mediators, the rise of doves in Aitolia and their diplomacy, and Philippos' approach to these Greeks. First, in the middle of the war against Carthage and Macedonia, Rome allied with Aitolia led by those with hawkish views toward Philippos. This alliance decreased his pressure on the republic by gaining the military support of the federation and its friends and riveting Philippos' attention on Greek affairs. Yet, the king, with his allies in the East, gained favourable results in the fighting around Greece from 209 onward. Several Hellenistic states, in this phase, appeared as mediators. They were actually apprehensive that a decisive victory for Philippos would lead to subjection not only of the Aitolians and their friends but all the Greeks. If Rome had paid attention to the aim of the mediators and given more support to Aitolia, these three would have co-operated against Macedonia. But the Romans did not notice or disregarded it. They were content with riveting Philippos' concerns on Greece. This attitude led the mediators to argue before the Aitolians that their alliance with the Romans would cause disaster to all Greeks, and that the federation should annul it and make peace with Macedonia, one of the Hellenistic states. It is important that this was partly a result of antipathy of the mediators to Rome but was generally the best possible tactic to control Philippos' increasing power in the circumstances. In order to manage his rise, it was better to lead Aitolia to make peace with Macedonia before this federation would be defeated decisively. Second, such a tactic of the mediators was also favourable to the Aitolians, in particular the opponents of the hawks. The argument of the mediating states enabled them to rise as the doves in Aitolia, and the federation jtself to make an honourable peace with Philippos. Labelling Rome an enemy of Greece gave the opponents of the hawks a good reason to oust the hardliners leading Aitolia to fight with Rome against Macedonia from the centre of the federation, and to have friendly contacts with the kingdom. Based on many Aitolian inscriptions, in 206/5 the federation was controlled by the doves and appears to have asked Macedonia to make peace not as a vanquished party but as a partner against Rome. Third, Philippos welcomed such a change in Aitolia, and soon made peace with the federation, which broke off with Rome, a decision clearly based on the cause of defending Greece. Other Aitolian allies had already retreated from the battlefield, and Rome was isolated in the East Yet, it was unfavourable even for Philippos to continue to fight against the republic. The hawks in Aitolia opposed to Macedonia were still strong. Continuation of war could trigger their rehabilita