since i dont have the map i cant answer the first half but Persia massive size would be a problem for Athens and Sparta however the Persians lost was their infantry is in poor quality compared to the Greek hoplites the Persian warrior is meant to engage targets on th opens planes of Asia and the middle east thats why they wore light to no amour also with Athens and Sparta at war with one another Xerxes thought they would not rally together and he could take them one at a time
