They were tasked with a frontal attack on the Greek positions. This first attack was bloodily repulsed by the Greeks. The Persians were unable to break through the phalanx line - they had to attack the Greeks from the front, leading the attack directly against the heavily positioned Greek phalanx. They could not attack from the wings, their cavalry had no way to charge. On subsequent attacks by the Persian army, the Greeks used the tactic of a sham retreat. When the Persians attacked, the hoplites would retreat and the Persian infantrymen would follow at full speed. Then the Greeks would make a rapid turn and strike at the surprised Persians, who additionally could not use archers because the troops were still in close quarters. The consequence was huge losses of Persian troops. At the end of the first day of fighting, Xerxes threw an elite unit of “Immortals” into battle, but they too were repulsed by the Hellenic hoplites.
