Finally, after the long wait, the Persians launched their attack.  The Greeks were defending the pass from behind a wall that blocked the road.  The Greeks took turns holding position behind the wall, as they fought off wave after wave of attacking Persians.  In the narrow space, the Persians could not make use of their greater numbers, meaning the Persians could only use small numbers of soldiers at a time to attack the Greeks.  In addition, the longer spears of the Greeks meant that they inflicted many deaths on the Persians.