Ancient history

Why did phalanx attack followed by a cavalry charge at Gaugamela?

There was no phalanx attack followed by a cavalry charge at Gaugamela. The battle was won by the Macedonian companion cavalry led by Alexander himself, who charged down the left wing of the Persian army and routed their cavalry, then wheeled around and attacked the fleeing chariotry and light horse of the Persian centre, while the phalanx held on against a charge from the Persian line infantry in front of them. No sources refer to a phalanx attack in this battle.