Alexander forded the Halys River in the summer of 333 BC, ending up on the border of southeastern Phrygia and Cilicia. He knew well the writings of Xenophon, and how the Cilician Gates had been impassable if obstructed by the enemy. Alexander reasoned that by force alone he could frighten the defenders and break through, and he gathered his men to do so. In the cover of night they attacked, startling the guards and sending them and their satrap into full flight, setting their crops aflame as they made for Tarsus. This good fortune allowed Alexander and his army to pass unharmed through the Gates and into Cilicia.