Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
Battle at Thermopylae - Greece Occupied by the Romans - Resistance of the Aetolians
Instead of returning with all speed to Asia and evacuating the field before an enemy in every respect superior, Antiochus resolved to entrench himself at Thermopylae, which he had occupied, and there to await the arrival of the great army from Asia. He himself took up a position in the chief pass, and commanded the Aetolians to occupy the mountain-path, by which Xerxes had formerly succeeded in turning the Spartans.
But only half of the Aetolian contingent was pleased to comply with this order of the commander-in-chief; the other 2000 men threw themselves into the neighbouring town of Heraclea, where they took no other part in the battle than that of attempting during its progress to surprise and plunder the Roman camp. Even the Aetolians posted on the heights discharged their duty of watching with remissness and reluctance; their post on the Callidromus allowed itself to be surprised by Cato, and the Asiatic phalanx, which the consul had meanwhile assailed in front, dispersed, when the Romans hastening down the mountain fell upon its flank.
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Reference address : https://www.ellopos.net/elpenor/rome/3-09-war-antiochus-asia.asp?pg=21