Chronicle of the Water Margin (alternatively known as Outlaws of the Marsh and All Men are Brothers), one of the Four Great Famous Works of Chinese literature, is a novel attributed to Shi Nai'an (施耐庵, ca. 1296–1372).
Apart from being a great read, it's obviously based on a historical background, eg. the campaigns against the Kithan Da Liao to the north are part of the plot.
Without entering into much details, what are the historical basis for Water Margin? What historical documents allude to the facts portrayed in the history? From the main characters (108 outlaws, Imperial forces and other outlaws), which ones are attested historically? If there's any example (apart from the supernatural), which aspect of the history is considered the most fictitious?