A phalanx is a military formation used in ancient warfare, particularly by the Greek armies. It consists of a group of soldiers standing close together in rows, often armed with long spears and shields. This tight arrangement allows for collective strength and protection, making it difficult for enemies to break through. The most famous example of a phalanx is the Macedonian phalanx, which was developed by Philip II and used effectively by his son, Alexander the Great. This formation emphasized discipline and coordination, enabling soldiers to work as a unified force on the battlefield.