The defeat of the Persians at Issus seems to have been due simply to the fact that, practically, the two adversaries engaged with almost equal numbers, and that the troops of Alexander were of vastly superior quality to those of Darhis.  The Asiatic infantry—­notwithstanding their proud title of “braves”—­proved to be worthless; the Greek mercenaries were personally courageous, but their inferior arms and training rendered them incapable of coping with the Macedonian phalanx.  The cavalry was the only arm in which the Persians were not greatly at a disadvantage; and cavalry alone cannot gain, or even save a battle.  When Darius put himself into a position where he lost all the advantages derivable from superiority of numbers, he made his own defeat and his adversary’s triumph certain.

It remained, therefore, before the Empire could be considered as entirely lost, that this error should be corrected, this false step retrieved.  All hope for Persia was not gone, so long as her full force had not been met and defeated in a fair and open field.  When Darius fled from Issus, it was not simply to preserve for a few months longer his own wretched life; it was to make an effort to redeem the past—­to give his country that last chance of maintaining her independence which she had a right to claim at his hands—­to try what the award of battle would be under the circumstances which he had fair grounds for regarding as the most favorable possible to his own side and the most disadvantageous to his adversary.  Before the heart of the Empire could be reached from the West, the wide Mesopotamian plain had to be traversed—­there, in those vast flats, across which the enemy must come, a position might be chosen where there would be room for the largest numbers that even his enormous Empire could furnish—­where cavalry and even chariots would be everywhere free to act—­where consequently he might engage the puny force of his antagonist to the greatest advantage, outflank it, envelop it, and perhaps destroy it.  Darius would have been inexcusable had he given up the contest without trying this last chance—­the chance of a battle in the open field with the full collected force of Persia.

His adversary gave him ample time to prepare for this final struggle.  The battle of Issus was fought in November, B.C. 333.  It was not till the summer of B.C. 331, twenty months later that the Macedonian forces were set in motion towards the interior of the Empire.  More than a year and a half was consumed in the reduction of Phoenicia, the siege of Gaza, and the occupation of Egypt.  Alexander, apparently, was confident of defeating Darius in a pitched battle, whenever and under whatever circumstances they should again meet; and regarded as the only serious dangers which threatened him, a possible interruption of his communications with Greece, and the employment of Persian gold and Persian naval force in the raising of troubles on the European side of the Egean.  He was therefore