War booty looted during the ‘Deluge’ continues to stir up a great deal of emotion. However, not all the artefacts held in Swedish cultural institutions share the same provenance – many have been purchased or received as gifts. After all, the Vasa dynasty sat on the Polish and Swedish thrones for several decades.

The Polish–Swedish wars and the plundering of the Polish-Lithuanian Commonwealth, as well as the shared Vasa dynasty ruling on both the Polish and Swedish thrones, resulted in numerous contacts between these two countries and, consequently, an exchange of artefacts. The collection of Polish artefacts in Sweden has still not been fully documented, although attempts to catalogue it have been made on several occasions to date. A project is currently underway at the University of Warsaw aimed at cataloguing the first part of the war booty looted by Swedish troops during the ‘Deluge’ and the Great Northern War. Previous documentation and research efforts were usually limited to a specific group of items, most often books. However, it is important to trace the history of these research endeavours.

Paragraph 9 of the Treaty of Oliwa (1660) was crucial in this regard, stating: “All archives, public, municipal, judicial and ecclesiastical records, as well as the royal library, which were removed from the Kingdom of Poland and the Grand Duchy of Lithuania, shall be returned by the Swedish side; this restitution shall take place upon the exchange of ratifications or, at the latest, within three months of such exchange”. The primary aim here was to recover the royal book collections as well as the Crown Register, that is, the register of documents issued by the royal chancery. The fundamental difficulty in recovering the book collections and archival materials in the 17th century lay in the fact that Godfryd von Schröder, sent to Sweden with instructions to recover the plundered heritage, was unaware of the number of items he was seeking. Having obtained several chests of books and documents, including the Crown Register—which was of crucial importance to the Poles—he returned to the Polish-Lithuanian Commonwealth. A further attempt took place during the reign of John III Sobieski; at which time Szczęsny Morsztyn’s retinue was dispatched to Sweden; within this retinue, one of the Crown officers, Jakub Bernig (Bernik), was tasked with locating the books looted by the Swedish army during the ‘Deluge’. Bernig returned with some of the books that had been taken away in the mid-17th century.

Stanisław August Poniatowski sent Jan Chrzciciel Albertrandi to Sweden, instructing him to gather information about Polish collections there. It was then that the search, for the first time, extended beyond book collections and archival materials, and was not limited solely to war booty. Albertrandi compiled numerous volumes of copies and transcripts of original documents, which he took with him on his return journey.

The 19th-century research included, amongst other things, studies of the Copernicans and the Warmians. This research was conducted, amongst others, by the Toruń-born historian Leopold Prowe (1821–1887), Maksymilian Curtze (1837–1903) and Ludwik Birkenmajer. In 1914, the research was carried out by Eugeniusz Barwiński, Ludwik Birkenmajer and Jan Łoś. This was a response to the work carried out in 1852 by Beda Dudik (1819–1890), a Moravian historian who had been searching for artefacts of Czech literature looted by the Swedes during the Thirty Years’ War; all the books and archival materials he discovered were published in *Forschungen in Schweden für Mährens Geschichte*. During the expedition, the collections of libraries and archives in Uppsala, Stockholm, Lund, Linköping, Vestrås and Strängnäs, as well as Skokloster Castle, were examined, and a few previously unknown archival documents were discovered.

Further research in Sweden was carried out in 1955 by Professor Antoni Mączak and Professor Marian Małowist, commissioned by the Institute of History of the Polish Academy of Sciences. The aim of their work was to select archival materials for microfilming. As a result of this expedition, Polish collections were enriched with, amongst other things, microfilmed materials from the Extranea IX: Polen collection, the Krigshistoriska Handlingar, the Diplomatica and the Riksregistraturet. It should be noted, however, that due to limited funds, not all the material was copied at that time.