The article covers the history of the former Land and University Library in Prague (now the National Library) between 1939 and 1945. The activities of the library were to be supervised by a German commissioner appointed in 1940 – Josef Becker, First Director of the Prussian State Library. As his duties kept him primarily in Berlin, he appointed the younger Berlin bibliologist Carl Wehmer as his permanent deputy in Prague. Although their main task was clearly the Germanisation of the library, one cannot deny that they deserve some credit, for example for increasing the staff level of the institution. Yet their main merit lies in that many of the library collections seized by the Gestapo and other bodies were not shredded but taken to the Clementinum, the seat of the library. From 1943, they organised the evacuation of book collections to places outside of Prague, which was threatened by air raids. The transport was supervised by Emma Urbánková, the head of the department of manuscripts. Approximately 12,000 volumes of medieval manuscripts and printed Bohemica of the 16th–19th centuries were evacuated to Karlštejn Castle in wooden crates. They included the library’s most valuable manuscript – the Codex Vyssegradensis, a coronation evangeliary from the 11th century. At the castle, they were deposited in the Burgrave’s House as well as directly in the famous Chapel of the Holy Cross. The massive Zlatá Koruna (Golden Crown) monastery and the châteaux in Pohled and Horažďovice also served as depositaries for the book collections. By the beginning of 1945, a total of 582,000 volumes had been sent to these three premises. They included many historical book collections. The paper is accompanied by recently discovered photographs documenting the course of the book evacuation.