The Pezhetairoi (
Greek ) were the backbone of the
Macedonian army. They were Foot Companions (in Greek the "Pezos" means foot warrior, infantryman, and the "Hetairos" is the companion or friend).The
Macedonian phalanxes were made up almost entirely by pezhetairoi. Pezhetairoi were especially effective against enemy cavalry, as their long pikes could be used to impale enemies charging on horse-back. During Alexander's war with Persia, a need for cavalry arose, so mounted companions also started appearing around this time.
See more at Wikipedia.org...