After the defeats at Poltava and Perevolotjna in 1709, 23 000 prisoners of war from the Swedish army were deployed in Russia, many in Siberia. The real Swedish city was Tobolsk. The Swedes were relatively well educated and therefore played a major role locally. Engineers supervised construction work, and Swedish schools attracted Russian pupils. There were conflicts, but the Swedes' efforts were appreciated. This is still talked about in Siberian cities. For example, the mayor of Yekaterinburg, Yevgeny Rojzman, has a strong interest in history and is a great friend of Sweden. Conditions are described in diaries and letters. Many letters from and to Swedish prisoners of war were caught by Russian censorship. Since the Russian archives were opened in the 1990s, the letters have become available. The planned project will primarily make these letters available to Swedish, Russian and international researchers and the general public. An edition of some kind (as a book and/or in electronic form) is the natural product. The project can be expected to provide historians with new information. Above all, the letters seem to shed light on the prisoners' own situation, their thoughts and beliefs, but also on daily life. The peace of 1721 marked a significant change in Swedish history. The prisoners of war who returned home (about a quarter of them) probably played an important role in further historical developments, but their role has been insufficiently investigated. The hitherto censored letters offer a fortunate opportunity.