The monastery on Mount Cassino was founded in 530 by the famous founder of Western monasticism, Saint Benedict of Nursia, and became the first monastery of the future Benedictine order. The Chronicle of the Monastery of Montecassino is a first-class historical source. Leo of Marsican began the chronicle with a biography of the founder of the monastery, and his successor Peter the Deacon completed it in 1138. Both monks were the best experts on the codices stored in the library (the Montecassino monastery is famous for its largest and most valuable collection of ancient and early Christian literature in Europe). The chronicle reflects everything the most important events in the political and church life of Europe for the period covered. For a wide range of history buffs.