The Battle of Pydna 168 BC
The Macedonian king Perseus succeeded his father Philip V through intrigue after disposing of his bother. He married the daughter of the Odryssian king, making alliance with the Thracians. Still uncertain of his hold on the throne and to gain popularity he annulled debts and advocated land redistribution. That made him very popular among the indebted farmers of Greece who were reduced to serfdom from the oligarchic ruling fractions who in their turn were supported by the Romans. He also made an armed visit to Delphi as a show of strength and to propagandize his cause. Naturally worried about his behavior, the Romans declared war on him under the pretext of aiding their Aetolian allies. Perseus was a populist politician but a very bad general. He squandered all his advantages and allowed the Romans to invade Thessaly.
Emboldened by the success of his light troops in Kallinikon, he decided to offer battle in the plain of Pydna in ground suitable for his pikemen. The Romans had 38,000 men, of which 33,400 were infantry, including two legions. A third of their army was composed by their Aetolian allies who were strong in cavalry and owned a number of war elephants. The Macedonians fielded 44,000 soldiers, of which 21,000 were phalangites. Their best auxiliaries were Thracian peltasts armed also with their terrible romphaias. The cavalry numbers were roughly equal, at about 4,000 each.
The battle started from a small skirmish that was fought on account of a horse and was fought late in the day. Initially the phalanx drove off the legions as the pila had little effect and the gladioli could not fend off the pikes. But he Romans fought tenaciously until they were driven to the slopes of Olympus where the broken ground allowed the maniples to exploit the openings in the phalanx and slaughter the pikemen.
Perseus promptly fled along with his Thracian allies. Without an army, he later had to surrender to the Romans, who dragged him to a triumph in Rome before finally executing him. The way was now open for conquering the rest of Greece.
The battle even today is used for heated arguments about the battle systems used by the opponents but most arguments usually omit the presence of the elephants that must have given the Romans advantage against cavalry in one of the flanks. There is the possibility that the Romans managed to gain the upper hand in the wings and then rolled Perseus flanks. It is a fact that at that time Roman generals were as a rule better than their opponents.
Livy, xlv. 42
Plutarch, Aem. Paul. 37