St. George Decoded - The Historical George, page 6
Of all the sources I've found about our good knight, some are specific in identifying the original George, while others are somewhat vague. The specific case is of a Roman tribune, or soldier, or military bureaucrat in the Near East who converted to Christianity in the early 4th Century. During a period of persecution of Christians by the Emperor Diocletian, he supposedly tore up an edict of the Emperor and for this he was executed. Another identification suggests he was a disreputable bishop of the early Church who assumed the mantle of hero and martyr.
Whoever he really was, the first recorded mention of him was less than twenty years after he was martyred, and a cult revering him spread for the next two or three centuries far and wide. He became a major saint for the Church, and by the 15th Century his day was a major celebration, almost as important as Christmas is to us today.
What is not mentioned in any source I have accessed is that at precisely the time of the historical George, the Roman cult of Mithras was a serious rival to Christianity. This may have had a major bearing on the development of the legend.
But before we progress to decoding the legend, we need to know something about precessional astronomy, for the key to our good knight's story lies in the sky above us.