Alexander's legacy includes the cultural diffusion and syncretism which his conquests engendered, such as Greco-Buddhism. He founded some twenty cities that bore his name, most notably Alexandria in Egypt. Alexander's settlement of Greek colonists and the resulting spread of Greek culture in the east resulted in a new Hellenistic civilization, aspects of which were still evident in the traditions of the Byzantine Empire in the mid-15th century AD and the presence of Greek speakers in central and far eastern Anatolia until the Greek genocide and the population exchange in the 1920s. Alexander became legendary as a classical hero in the mould of Achilles, and he features prominently in the history and mythic traditions of both Greek and non-Greek cultures. He was undefeated in battle and became the measure against which military leaders compared themselves. Military academies throughout the world still teach his tactics. He is often ranked among the most influential people in history.