The Chronicle of Montecassino gives a detailed and compelling account of the monastery during its ‘golden age’ under Abbots Desiderius and Oderisius I, and the challenges that it then faced from the early years of the twelfth century onwards. As law and order in the Principality of Capua broke down, the monks faced increasing threats to their lands, and internal division arose within the monastery. Eventually too their previously close relationship with the papacy broke down. The last part of the chronicle includes a day-by-day account by Peter the deacon of his defence of the monastery at a meeting with Pope Innocent II and Emperor Lothar III in July 1137. This text provides a fascinating insight into both monasticism and politics in medieval southern Italy.