Battle of Thermopylae (191 BC)


The Battle of Thermopylae was fought in 191 BC between a Roman army led by consul Manius Acilius Glabrio and a Seleucid force led by King Antiochus III the Great. It was the first major battle of the Roman–Seleucid War. The Romans were victorious, and as a result, Antiochus was forced to flee from Greece.

Battle

At the outbreak of the war in 192 BC, Antiochus crossed from Asia Minor to Greece with a small force, expecting the various states in the region to support him as a fellow Hellene in resistance to Roman hegemony. However, only the Aetolian League actually joined forces with Antiochus; other states either remained neutral or sided with the Romans. Antiochus managed to capture some cities in Greece, but was unable to obtain reinforcements from Asia before in 191 BC a large Roman army under the consul Manius Acilius Glabrio crossed from Italy and advanced on his position.
Knowing he was outnumbered around 2:1 by the approaching Roman army, Antiochus hoped to use the narrow pass at Thermopylae to his advantage, taking inspiration from the earlier Greek city-states' stand against the much larger Persian army at the Battle of Thermopylae. However, the path the Persians had used to outflank the Greeks on that occasion was by now relatively well known. Antiochus therefore stationed his allied Aetolian troops in the hills above the pass in an attempt to avoid being outflanked, whilst the main body of his Seleucid army occupied the pass itself.
While the main Roman and Seleucid forces fought inconclusively in the narrow pass, two Roman detachments were sent to dislodge the Aetolians from two of the hills. Acilius Glabrio gave command of these forces to two senior legates: Lucius Valerius Flaccus and Marcus Porcius Cato, both former consuls. Flaccus' force was defeated, but Cato's was able to push the Aetolians off the high ground and attack the Seleucid camp from behind. This sparked a panic among the Seleucid forces, who fled from the battlefield. Roman sources claim that almost the entire Seleucid force of 10,000 was killed, captured, or surrendered, either on the battlefield or over the following few days of pursuit, whilst the Romans lost only 200 men.
The immediate result of the Roman victory was to eject Antiochus from Greece, whilst the Aetolians were forced to sue for peace.

Ancient sources

The battle was described by Appian and by Livy 36.16-19.
Appian's account: