Philip V's strategy of consolidating and extending his despotic rule over the free cities cities in Greece the Aegean and the coast of Asia Minor (Turkey) was scarcely disguised.
In 201 BC he carried carried troops across the Hellespont and set about the conquest of Caria. He was alas driven back by the stiff joint resistance by the fleet of Rhodes and Attalus, king of Pergamum.
This moment of weakness proved disastrous to Macedon as it saw Athens and other Greek cities seeing their chance of ridding themselves of Macedon rule. The Greek cities broke away and appealed to Rome for help (200 BC).
After the hardships of the struggle against Hannibal, the Roman people had had enough of fighting. And yet the senate was convinced that the choice was not before war and peace, but between war in Macedon or in Italy. For sooner or later Philip would attack. So Rome chose war.
Though the Roman campaigns if 200 and 199 BC were ineffective. In 198 BC the command of the Roman and allied army was granted to Titus Quinctius Flaminius, and Rome's choice proved to be a wise one.
He succeeded in winning over the Achaean League, which had been reluctant to join forces with the Aetolian League of Greek cities.
Then, in 197 BC Flaminius was able to bring Philip of Macedon to a decisive engagement at Cynoscephalae in Thessaly, where the infamous Macedonian phalanx was decisively defeated by the Roman legions.
Battle of Cynoscephalae
After Cynoscephalae Flaminius could dictate his own terms - to his Greek allies as much as to the defeated Macedons.
Though as Flaminius left Greece two years later, the Aetolians, Rome's closest allies during the contest, had been treated with little respect and were left angry at Rome. Though powerless to act against her, they and others among the Greek cities found a new ally in the ambitious king of Syria, Antiochus, who was had benefited from Macedon's weakness by seizing the Greek cities in Asia which Philip had been forced to withdraw from.
In 192 BC the Greek cities of the Aetolian League rose up against Rome, but of the three cities in which the Romans had garrisons they only succeeded in capturing the city of Demetrias.
With equal recklessness Antiochus cast aside the invaluable advice he was receiving from Hannibal who as residing at his court and invaded Greece with a totally insufficient force.
The end of ths desperate scheme was not long in coming. Early in the next year (191 BC) Roman armies, with the co-operation of Philip V of Macedon, were entering Thessaly. To protect the south Antiochus occupied the historic pass of Thermopylae.
But just as with Leonida's famous Spartans of old, the almost impregnable pass was taken by a separate force which forced its way over the hill and fell into the rear of the defenders.
Antiochus escaped with only a remnant of his army left alive and set over to Asia.
Rome enters Asia for the first time at the Battle of Magnesia
But the Romans, under the command of Lucius Scipio followed him there, after a combined effort by Rome and Rhodes, defeating the Phoenician fleets at the sea-battle Myonnesus.
Near Magnesia the Roman army met with a huge, but ill disciplined army of Antiochus.
The Roman victory was complete, ancient sources numbering the losses of Antiochus at 53000 men, and the Roman losses at four hundred. Antiochus escaped with his life but could only sue for peace, but under the terms for peace he had to agree to surrender his fleet and war elephants and all his territorial possessions north of the Taurus mountains, as well as paying Rome a substantial amount.
Rome as a conqueror of the aggressive king of Syria, exercised her right of distributing the territories from which she had ejected him. However, Rome did not yet claim any Asiatic territory for herself. Hence all the lands were shared out between Pergamum and Rhodes, Rome's close allies in this campaign.