Plutarch Sertorius 12

[1] By these devices he made the people tractable, and so found them more serviceable for all his plans; they believed that they were led, not by the mortal wisdom of a foreigner, but by a god. At the same time events also brought witness to this belief by reason of the extraordinary growth of the power of Sertorius.

[2] For with the twenty-six hundred men whom he called Romans, and a motley band of seven hundred Libyans who crossed over into Lusitania with him, to whom he added four thousand Lusitanian targeteers and seven hundred horsemen, he waged war with four Roman generals, under whom were a hundred and twenty thousand footmen, six thousand horsemen, two thousand bowmen and slingers, and an untold number of cities, while he himself had at first only twenty all told.

[3] But nevertheless, from so weak and slender a beginning, he not only subdued great nations and took many cities, but was also victorious over the generals sent against him: Cotta he defeated in a sea-fight in the straits near Mellaria; Fufidius, the governor of Baetica, he routed on the banks of the Baetis with the slaughter of two thousand Roman soldiers; Lucius Domitius, who was pro-consul of the other Spain, ¹ was defeated at the hands of his quaestor;

[4] Thoranius, another of the commanders sent out by Metellus with an army, he slew; and on Metellus himself, the greatest Roman of the time and held in highest repute, he inflicted many defeats and reduced him to so great straits that Lucius Manlius came from Gallia Narbonensis to help him, and Pompey the Great was hurriedly dispatched from Rome with an army.

[5]
  For Metellus was at his wits’ end. He was carrying on war with a man of daring who evaded every kind of open fighting, and who made all manner of shifts and changes, owing to the light equipment and agility of his Iberian soldiers; whereas he himself had been trained in regular contests of heavy-armed troops, and was wont to command a ponderous and immobile phalanx, ² which, for repelling and overpowering an enemy at close quarters, was most excellently trained, but for climbing mountains, for dealing within the incessant pursuits and flights of men as light as the winds, and for enduring hunger and a life without fire or tent, as their enemies did, it was worthless.