Do you even know that an Indian contigent of Brahmins actually fought alongside Drius against Alexander? Do you know that even today we have place in Iraq, close to Baghdad called Al-Hindiya? We had a permanent garrison there of Brahmin warriors. Drius was able to escape the Battle of Gaugamela only because of this unit of Indian Brahmin cavalry? Please read about it.
Battle of Gaugamela - Wikipedia
Alexander could have pursued Darius at this point. However, he received desperate messages from Parmenion (an event that would later be used by
Callisthenes and others to discredit Parmenion) on the left. Parmenion's wing was apparently encircled by the cavalry of the Persian right wing; being attacked from all sides, it was in a state of confusion.
Alexander was faced with the choice of pursuing Darius and having the chance of killing him, ending the war in one stroke but at the risk of losing his army, or going back to the left flank to aid Parmenion and preserve his forces, thus letting Darius escape to the surrounding mountains. He decided to help Parmenion, and followed Darius later.
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While holding on the left, a gap had opened up between the left and center of the Macedonian phalanx, due to Simmias' brigade of
pezhetairoi being unable to follow Alexander in his decisive attack, as they were being hard-pressed.
The Persian and Indian cavalry in the center with Darius broke through. Instead of taking the phalanx or Parmenion in the rear, however, they continued towards the camp to loot. They also tried to rescue the Queen Mother,
Sisygambis, but she refused to go with them. These raiders were in turn attacked and dispersed by the rear reserve phalanx as they were looting.
What happened next was described by Arrian as the fiercest engagement of the battle, as Alexander and his companions encountered the cavalry of the Persian right, composed of Indians,
Parthians and "the bravest and most numerous division of the Persians", desperately trying to get through to escape. Sixty Companions were killed in the engagement, and
Hephaestion,
Coenus and Menidas were all injured. Alexander prevailed, however, and Mazaeus also began to pull his forces back as Bessus had. However, unlike on the left with Bessus, the Persians soon fell into disorder as the Thessalians and other cavalry units charged forward at their fleeing enemy.