Plutarch, Sertorius
Bernadotte Perrin, Ed.

3. To begin with, when the Cimbri and Teutones invaded Gaul,¹ he served under Caepio, and after the Romans had been defeated and put to flight, though he had lost his horse and had been wounded in the body, he made his way across the Rhone, swimming, shield and breastplate and all, against a strongly adverse current; so sturdy was his body and so inured to hardships by training. [2] In the next place, when the same enemies were coming up with many myriads of men and dreadful threats,² so that for a Roman even to hold his post at such a time and obey his general was a great matter, while Marius was in command, Sertorius undertook to spy out the enemy. So, putting on a Celtic dress and acquiring the commonest expressions of that language for such conversation as might be necessary, he mingled with the Barbarians; and after seeing or hearing what was of importance, he came back to Marius. [3] At the time, then, he received a prize for valour; and since, during the rest of the campaign, he performed many deeds which showed both judgement and daring, he was advanced by his general to positions of honour and trust. After the war with the Cimbri and Teutones, he was sent out as military tribune by Didius the praetor to Spain,³ and spent the winter in Castulo, a city of the Celtiberians. [4] Here the soldiers shook off all discipline in the midst of plenty, and were drunk most of the time, so that the Barbarians came to despise them, and one night sent for aid from their neighbours, the Oritanians, and falling upon the Romans in their quarters began to kill them. But Sertorius with a few others slipped out, and assembled the soldiers who were making their escape, and surrounded the city. He found the gate open by which the Barbarians had stolen in, but did not repeat their mistake; instead, he set a guard there, and then, taking possession of all quarters of the city, slew all the men who were of age to bear arms. [5] Then, when the slaughter was ended, he ordered all his soldiers to lay aside their own armour and clothing, to array themselves in those of the Barbarians, and then to follow him to the city from which the men came who had fallen upon them in the night. Having thus deceived the Barbarians by means of the armour which they saw, he found the gate of the city open, and caught a multitude of men who supposed they were coming forth to meet a successful party of friends and fellow citizens. Therefore most of the inhabitants were slaughtered by the Romans at the gate; the rest surrendered and were sold into slavery.