After Emma and Antonia Bunzel ceded title to Thürnthal Castle near Fels am Wagram to the German Reich at the end of June 1943 under the 11th Regulation to the Reich Citizenship Law, the Oberfinanzpräsident for Vienna and Lower Danube took over administration of the building complex. The Institute for Monument Preservation in Vienna was allowed to use the castle as a depot for the duration of the war. The depot manager was Adolf Graf sen., the Institute's joiner. The Vienna architect Josef Friedl was commissioned to plan the repair and conversion work on the baroque castle, a listed building since 1939 but in extremely dilapidated condition. Among the reasons for converting the castle into a protected depot was an order by Hitler to evacuate from Vienna the entire Anton Lanckoronski collection, which was now exclusively reserved for the "Führer", despite claims by Reich Marshal Hermann Göring and the Haupttreuhandstelle Ost. The results of the investigation by the chemist Maximilian Eder in November 1943, which determined that the humidity on the first two floors, where several paintings were already stored, was too high, did not prevent Herbert Seiberl, head of the Institute for Monument Preservation responsible for salvaging, from stepping up the work in Thürnthal. The billeting of French prisoners of war in the south wing of the castle also apparently did not conflict with the storage principle of separating people and objects. By the end of the year, the artworks stored since 1942 at Immendorf Castle and Anton Lanckoronski's library from Vienna, the library of the Institute for Monument Preservation and the War in Heaven group from the portal of St Michael's Church in Vienna were moved there. In early 1944 the large-format paintings for the "Führermuseum" in Linz were transferred there from Kremsmünster Benedictine Abbey. Objects managed and stored by the monuments authority that had been seized from the collections of Serena Lederer, Albert Pollak, Otto Pick, Markus Lindenbaum, David Goldmann, Emil Karpeles-Schenker and Elisabeth Fischer, and the remainder of the seized Rothschild collections in Vienna that had not been distributed were also stored there before being transferred to the salt mine in Altaussee. From May 1944 the castle also served as a depot for thousands of objects taken from the collection of Baron Jean Cassel van Doorn in France by order of the Reichsleiter Rosenberg Taskforce and stored in Thürnthal and Altaussee under the code name "Aktion Berta". Despite several air raids on the nearby airfield at Fels am Wagram, the removals and evacuations from Vienna continued. In July 1944 the eight-section Beethoven Frieze by Gustav Klimt from the Lederer collection was stored in the castle chapel. The last transports from Vienna included the remains of the seized collection belonging to Rudolf Gutmann, which until then had been stored at the depot of the Institute for Monument Preservation in the Lower Belvedere Orangery. The transfer from Steyersberg Castle planned for February 1945 did not take place because of the weather conditions and the absence of vehicles. After the war the Thürnthal depot was administered by Soviet occupation troops and was seized with its contents in late July 1946 by the Landeskommandantur der Roten Armee für Niederösterreich. After several rounds of negotiations by the Austrians, goods in the depot with demonstrable Austrian provenance were finally released in December 1946 and transferred to the monuments authority depot. After the handing over of the objects from "Aktion Berta" to the French authorities in August 1947, the castle was emptied, except for the Beethoven Frieze, which was not transferred to Altenburg Abbey until August 1956, and some other residual items. In April 1950 Thürnthal Castle and its grounds and annexes were restored to the former owner Emma Barber, née Bunzel, who had fled to Britain in July 1938. Her sister and former co-owner of the castle, Antonia Bunzel, and her father Guido Bunzel were murdered in 1942 in Maly Trostinec.