In this History, thanks to the ancient and modern historical writings and the research of archives, the fundamental themes of the medieval history of Siena are well defined, the ones that were and are still today most important. The merchants and the masters of country estates, the powerful growth of the 13th century with Montaperti and the eternal rivalry with Florence, the magnificent Nine, Saint Catherine, Saint Bernard and Pius II, the oppressive Pandolfo Petrucci, The battle of Camollia and the glorious and tragic end to the Republic.