It has been stated that Parmenion counselled a night attack in 331 BC on Darius' assembled superior forces at the Battle of Gaugamela, which Alexander took as evidence that Darius would keep his troops at the ready through the night and offer the Macedonians some advantage if they rested for a battle in daylight. During the battle, Parmenion led the Pezhetairos on the left flank which had been hurt by an opening made by Alexander's speedy advance with the cavalry. In Plutarch's Parallel Lives it is further suggested the escape of Darius was due to Parmenion's "sluggish and ineffectual" leadership, or even that he was jealous of Alexander's successes.