Plutarch, Caesar
Bernadotte Perrin, Ed.

40. This emboldened the soldiers of Pompey and the leaders by whom he was surrounded to keep close to Caesar, whom they thought defeated and in flight. For Pompey himself was cautious about hazarding a battle for so great a stake, and since he was most excellently provided with everything necessary for a long war, he thought it best to wear out and quench the vigour of the enemy, which must be short-lived. For the best fighting men in Caesar's army had experience, it is true, and a daring which was irresistible in combat; [2] but what with their long marches and frequent encampments and siege-warfare and night-watches, they were beginning to give out by reason of age, and were too unwieldy for labour, having lost their ardour from weakness. At that time, too, a kind of pestilential disease, occasioned by the strangeness of their diet, was said to be prevalent in Caesar's army. And what was most important of all, since Caesar was neither strong in funds nor well supplied with provisions, it was thought that within a short time his army would break up of itself.