The document summarizes hoplites and the phalanx formation used in ancient Greece during the Persian Wars of the 5th century BCE. It describes the armor and training of hoplites, allowing them to fight in tight, overlapping formations called phalanxes that provided protection from spears and arrows. The phalanx formation marched forward as a unified wall of shields. It then briefly outlines some of the key battles between Greece and Persia, including Marathon, Thermopylae, Salamis, and Plataea, where the phalanx formation and Greek naval forces proved effective against the Persian invaders.