Greek mercenaries are professional warriors who surpassed the rest of the world in martial art, which generated a demand for their use in other countries. This book presents the history of the transformation of the army of "amateur" soldiers from their initial primitive state in ancient times (VII century BC) into a developed organized force in the Hellenistic era. Mercenaries recruited from ethnic Greeks were attracted to the service of the states of the Mediterranean and the Middle East and played a significant role not only in military expeditions, but also in the social and political history of the eras of Cyrus the Younger, Dionysius I, Philip II and other tyrants and autocrats. It was they who contributed to the formation and defense of the empire of Alexander the Great.