Originally Posted by Galerius' Ghost
I like Goldsworthy but I have to disagree here. Caesar himself states that his right wing had disintegrated and was routing in panic. While it is true that the area around Dyrrachium was a 'maze' of trenches and fortifications, from the description of events it doesn't seem that Caesar's men were likely to reform and fight, if Pompey had followed up hard on their heals. Its very hard to regain control of an army once panic has ensued and this is typically when most casualties were inflicted during ancient battle. I understand Pompey was wary of engaging Caesar's veteran troops in open battle and would have rather fought a war of attrition, but as history shows, there was to be a decisive battle. Pompey heavily outnumbered Caesar at Dyrrachium and once Caesar's army began to give way Pompey should have followed through and attempted to end the whole thing while he held the advantage. Caesar, himself, seems to have thought Pompey should have followed up, as well.
On Caesar's opinion... it's very hard to say. We have from other sources a quote from him about how Pompey "would have won if he knew how to conquer", but such a remark, if he made it, probably goes along with the remark he made after the battle of Zela, where after flooring Pharnaces in four hours of vicious fighting he commented that Pompey had been very lucky to be considered a great general for fighting foes of this calibre. Caesar was not above trying to deflate his rival's reputation somewhat.
Getting back to Dyrrachium, it's not as simple a chain of events as Pompey breaking through and then holding back when he should have kept attacking. He broke through, then Caesar and Mark Antony arrived on the scene and attempted to remedy the situation. Both sides built more fortifications - Pompey to secure his new gains, Caesar to try and plug the hole (he had Mark Antony built another whole camp beyond the spot where Pompey had broken through. After a while Caesar believed he saw an opportunity for a counter-attack, and lead it, but Pompey eventually managed to get there with 5 legions and Caesar's force panicked and routed. This is the moment when Pompey supposedly misses an opportunity to follow up. But this doesn't quite ring true for me (or, apparently, for Goldsworthy). Caesar had just come out of at least several intense hours of building new fortifications to plug the line, and his routing forces would have retreated back inside to presumably rally. In any case, the force with him that had just been routed consisted of only a few thousand men at most - the rest of his forces, somewhere in the area of 25,000 men, were still ready at their posts to be brought up. Caesar's own failed counter-attack had shown just how easy it was for the maze of fortifications to foul up an attack that had been going well.
It should be remembered that Pompey had concentrated here some 5-6 legions and a lot of cavalry - a large portion of his forces, If he took a gamble here and tried a follow-up and it went wrong then he would find himself in a far worse position than Caesar was in at the moment.
All in all, Pompey would have found plentiful reasons beyond just excessive caution not to attempt a follow-up.