イッソスの戦い
Darius did not take the field against Alexander's army until a year and a half after Granicus, at the Battle of Issus in 333 BC. His forces outnumbered Alexander's soldiers by at least a 2 to 1 ratio, but Darius was still outflanked, defeated, and forced to flee. It is told by Arrian that at the Battle of Issus the moment the Persian left went to pieces under Alexander's attack and Darius, in his war-chariot, saw that it was cut off, he incontinently fled – indeed, he led the race for safety. On the way, he left behind his chariot, his bow, and his royal mantle, all of which were later picked up by Alexander. Greek sources such as Diodorus Siculus' "Library of History" and Justin's "Epitoma Historiarum Philippicarum" recount that Darius fled out of fear at the Battle of Issus and again two years later at the Battle of Gaugamela despite commanding a larger force in a defensive position each time. At the Battle of Issus, Darius III even caught Alexander by surprise and failed to defeat Alexander's forces. Darius fled so far so fast that Alexander was able to capture Darius’ headquarters and take Darius’ family as prisoners in the process. Darius petitioned to Alexander through letters several times to get his family back, but Alexander refused to do so unless Darius would acknowledge him as the new emperor of Persia.