The battle of Aous (probable date 24 June 198 BC) was the first significant Roman victory during the Second Macedonian War. In 200 BC a Roman army had landed at Apollonia, on the eastern shores of the Adriatic, and in the following year had raided western Macedonia.
Philip could not allow a repeat of the events of 199, and so in the spring of 198 BC he took up a strong defensive position on the Aous River, defending a gorge close to Antigoneia (modern Vijose in Albania). This blocked the best route into Macedonia from the west.
The Roman commander at the start of 199, P. Villius Tappulus, decided to attack Philip, and had advanced to within five miles of his position when his replacement arrived. This was Titus Quinctius Flaminius, one of the consuls for 198 BC, a man with some experience of Greece.
His arrival was followed by direct negotiation with Philip. The Macedonian king had finally realised how dangerous the Romans could be now that the end of the Second Punic War had left them free to concentrate on the war in Macedonia, and so offered to accept the original Roman terms of 200 BC – to surrender those cities around the Aegean that he had conquered.
Unfortunately for Philip, the Romans were not interested in peace on these terms – their real war aim was to reduce the power of Philip, who had never been forgiven for his declaration of war in 215 BC, at the height of the Second Punic War. Flaminius now demanded that Philip should abandon Thessaly, an area that had been ruled by the Macedonians for a century and a half. Unsurprisingly Philip ended the conference and withdrew to his apparently impregnable position in the Aous gorge.
Philip’s bad luck continued. The Romans were provided with a local guide by Charops, a powerful Epirote. With the guide’s help 4,300 Roman solders marched around Philip’s position and threatened to trap him in the gorge (probably on 24 June 198 BC). Philip realised his danger just in time, and managed to escape from the trap. The fighting cost him 2,000 men, all of his baggage, and left Thessaly exposed to the Romans.
In the aftermath of their victory on the Aous, the Romans advanced into Thessaly, where they captured a number of towns, before turning south to over-winter on the Corinthian Gulf. The Roman successes also convinced the Achaean League to ally with them, ending their long alliance with Macedonia.