The early Greek city states often fought on narrow valley floors, where cavalry was not so important. Often, there was little or no cavalry. But in the Greco-Persian Wars, the battles were fought on more open land, where cavalry was a great force. An example of this is the Battle of Gaugamela. There, Alexander manoeuvered to the right to prevent a double envelopment from the Persian army. Darius commanded his cavalry on his left flank to check the oblique movement of the Greeks by attacking their cavalry. Alexander's Companion cavalry then charged the weakened enemy center where Darius was posted and were followed by the phalanx formation.