A red standard with the image of Saint George riding a horse and striking a dragon was Genoa's Republic flag until the first half of XIII century, when it began to be replaced by a red cross on a white field. It assumed a modern rectangular shape, with no tails, from mid of XIV century. Saint George's flag remained as the official flag of the Republic both on land and sea until its very end, when invaded by the French revolutionary army (1797).
Sources: Anonymous manuscript from 1670, reprinted in Amsterdam 1966 as «Flags of the World 1669-1670» | «Flags of The World» (FOTW) website:Genoa (Liguria, Italy)