The diary of Jan Peter Sapieha occupies a special place among the memoirs of the troubled times of the beginning of the 17th century. It is one of the few works written in hot pursuit of events. Throughout the stay of Jan Sapieha in Russia, his secretaries, in the spirit of ancient traditions, day after day described the actions of the hetman and the soldiers of his army. After the death of their leader, the Sapezhins took the diary along with an extensive archive to the Polish-Lithuanian Commonwealth, where by the middle of the 17th century the archive was divided into several documentary collections, which were deposited in different ways in the libraries and archives of Poland, Russia, Ukraine, Sweden.