Xerxes was the new king of Persia and he was motivated to conquer Athens because of his father, Darius', death. Xerxes spent 10 years rebuilding the Persian army. In 480 B.C. they came into Athens through land. There were only 7,000 Greeks and 300 of them were Spartans. There were many, many more Persians. The Greeks at this point knew that they were going to loose and so they told everyone to retreat. The Spartans did not retreat because they had a code that they lived by that said, come back victorious or come back on your shield. All of the Spartans stayed and they all were killed. This event was called the Sacrifice of the Spartans and it gave Athens time to prepare themselves for war. Athens positioned themselves into a naval battle. They led Persia to the Island of Salimis and there was a hard sea to navigate surrounding it. Persia was a land based military and when they found themselves in a naval battle they didn't know what to do. They ended up loosing and Athens was only victorious because they outsmarted Persia. The Persian army them spent a year retreating.