In the spring of 331 B.C. the king went back to Tyre, and by August he had reached Thapsacus, a town on the banks of the river Euphrates. He wished to go on to Babylon, the capital of the Persian empire, but the direct way to the city, which was down the Euphrates, was guarded by Cyrus with a large army. So Alexander struck off across the north of Mesopotamia, and reaching the Tigris marched along the river on the eastern side. Above Nineveh he crossed to the other bank, and after marching southward for several days, he heard that Darius was encamped on a plain near Gaugamela, on the river Bumōdus.
Even to the brave Macedonian generals, the vast hosts of the Persians looked formidable.
Parmenio looking at them begged the king to surprise the enemy by a night attack rather than risk a battle in daylight.
‘I will not steal a victory,’ answered Alexander.
The night before the battle the king slept soundly, as though nothing preyed upon his mind. In the morning his generals found him still fast asleep, so without disturbing him they themselves bade the soldiers have breakfast.
At length Parmenio went to wake the king, and having with difficulty roused him, he asked how it was possible he could sleep so soundly when the most important battle of his life had to be fought that day.
‘You slept, sire, as though you were already victorious,’ said the anxious general.
‘Are we not so indeed,’ answered the king, ‘since we are at last relieved from the trouble of wandering in pursuit of Darius, through a wide and wasted country, hoping in vain that he would fight us?’
Alexander, who was already dressed, now put on his helmet, which was of iron, yet so polished was it that it shone as silver. Great skill had been lavished on the decoration of his belt, which was indeed the most splendid part of his dress. He then ordered his army to be drawn up in battle array, while he mounted Bucephalus, who was old now, yet eager for battle.
Before the king gave the signal to attack, he stretched out his right hand to heaven, and called upon the gods to defend and strengthen the Greeks, if he indeed were the son of Zeus.