Plutarch of Chaeronea (46-c.122): influential Greek philosopher and author, well known for his biographies and his moral treatises. His biography is here; the following fragment is from his Life of Julius Caesar.
In the last days of 50, civil war between Pompey and Julius Caesar became inevitable. In chapter 28 of his Life of Julius Caesar, the Greek author Plutarch of Chaeronea describes what the two men thought in these weeks.
The translation below was made by Robin Seager.
[28.1] Caesar had long ago decided that Pompey must be removed from his position of power; and Pompey, for that matter, had come to just the same decision about Caesar. Crassus, who had been watching their struggle, ready to take on the winner himself, had been killed in Parthia; so that now the field was clear. The man who wanted to be on top had to get rid of the one who at present held that position: the man who was for the moment on top had, if he wished to stay there, to get rid of the man he feared before it was too late.
[28.2] It was only recently that Pompey had come to fear Caesar. Up till this time he had despised him. It was through his influence, he thought, that Caesar had grown great, and it would be just as easy to put him down as it had been to raise him up.
[28.3] But Caesar's plan had been laid down from the very beginning. Like an athlete he had, as it were, withdrawn himself from the ring and, in the Gallic wars, had undergone a course of training. In these wars he had brought his army into perfect condition and had won such fame for himself that he had now reached a height where his own achievements could challenge.