In people’s curiosity over King Arthur, the fact that he lived in an heroic age is often overlooked. But I think knowing that and understanding it are fundamental to grasping the world he lived in and the means by which his accomplishments were remembered. The Heroic Age is a phenomenon which is widespread in Indo-European history but is not limited to that culture. A quick run-down of histories many manifestations should give you a better idea of the concept.
Sumerian: Very little is known about the earliest recorded heroic age. It extended from 2700 to 2500 B.C.E., when several of the city-states of Mesopotamia, most notably Gilgamesh, battled each other in constant warfare. A limited number of tales about them have survived. However, archeological evidence demonstrates that all the remembered heroes of legend in this era were historical characters.
Indian: This era is remembered chiefly for the events found in the Mahabharata. The range of the period is unknown, though it probably took place between 1100 and 1800 B.C.E. Several of the characters in the epic are named in king-lists and for that reason are considered historical.
Greek: Probably all of the Trojan Wars took place in this era, traditionally between and inclusive of the Argonauts and the destruction of Troy, roughly 1400 and 1200 B.C.E. Historically it is known that Troy fell in this period but also that the entire Mediterranean region suffered an extended agricultural collapse. The traditional records among the Greek city-states consistently name heroic age kings as their rulers in within a long list of kings.
Irish: Traditionally set in the first century before the common era and focusing on Conchobar and his most famous warrior Cu Chulainn. The tales involve the local infighting of many kings. There is no known reason for the inception of the heroic age, but the island is poorly recorded in this era.
Persian: Focusing on the third century to the first century before the common era as well as Prince Rustam, the period was characterized by regular skirmishes against nomads, especially the Tochari and the Indo-Scythians. Historically it began with the break-up of Alexander’s empire and ended when the Parthians conquered the area.
Germanic: The culture began its heroic age with the invasion of the Germanic tribes into Europe in search of land, food, and supplies and ended with the development of stable kingdoms, ca. 350-600. Several key heroic age figures, including Beowulf, Hrolf Kraki, and Sigurd, are accepted as historical figures because of complementary historical and archeological information.
British: Arthur’s heroic age began with the rise of kingships in response to continuing Germanic settlements on their lands and continued until cattle raiding was generally replaced with large-scale warfare, ca. 470-600. Apart from Arthur, a host of figures who appear in praise poetry and folkloric materials are generally accepted as historical.
Some points of comparison? Where anything is known about the beginning of an heroic age it is the result of an economic or political calamity, e.g. plague or some sort of political disintegration. This is so with the British Heroic Age. In all cases but the British the central characters have all been alternatively proven as historical characters. And perhaps as coincidence and perhaps not, most known heroic ages occurred in Indo-European cultures.