Simplify the following text for a Grade 8 native English-speaking person.
Original: The Battle of Salamis ( , Naumachia tÄ `` s Salaminos ) was fought between an Alliance of Greek city-states and the Persian Empire in September 480 BC in the straits between the mainland and Salamis , an island in the Saronic Gulf near Athens .
Simplified: The Battle of Salamis was a battle between an Alliance of Greek city-states and the Achaemenid Empire of Persia . It happened in September 480 BC in the straits between the mainland and Salamis Island .