After what battle with Alexander the Great did the Persian kingdom cease to exist?

In 331 BC. e. after numerous victories, the troops of Alexander the great approached the wide plain between the Tigris and the Euphrates. The Persian army of Darius III was already waiting for the enemy and was ready for his attack. Alexander the Great did not immediately engage the Persians. His army settled in a huge camp near the village of Gavgamela. The night of anxious expectation of an attack from the Macedonians drained the moral strength of the Persians. The soldiers of Darius felt fear of the powerful force of the Macedonian army. The battle began and for Darius III it was the last. The army of the Persians that remained without a leader was defeated by Alexander the Great. The victory of the Macedonians meant the collapse of the once mighty empire of the Persians.