The Paper Brigade was the name given to a group of residents of the Vilna Ghetto who hid a large cache of Jewish cultural items from YIVO (the Yiddish Scientific Institute), saving them from destruction or theft by Nazi Germany. Established in 1942 and led by Abraham Sutzkever and Shmerke Kaczerginski, the group smuggled books, paintings and sculptures past Nazi guards and hid them in various locations in and around the Ghetto. After the Ghetto's liquidation, surviving members of the group fled to join the Jewish partisans, eventually returning to Vilna following its liberation by Soviet forces. Recovered works were used to establish the Vilna Jewish Museum and then smuggled to the United States, where YIVO had re-established itself during the 1940s. Caches of hidden material continued to be discovered in Vilna into the early 1990s. Despite losses during both the Nazi and Soviet eras, 30–40 percent of the YIVO archive was preserved, which now represents "the largest collection of material about Jewish life in Eastern Europe that exists in the world". YIVO and the Brigade Prior to the Second World War, the city of Vilna was a hub of Jewish activity and learning, to the point where it was nicknamed the "Jerusalem of Lithuania". Seen as the central melting pot of Jewish tradition and Yiddish culture, the city was the home of YIVO, an organisation established in 1925 to preserve and promote Yiddish culture. Based in the Pohulanka district, YIVO maintained an extensive archive of Yiddish language works and other books relating to Jewish culture and history in its headquarters. With the capture of Vilna by Soviet forces on 19 September 1939, the organisation was (in sequence) taken over by Soviet forces, with Moyshe Lerer installed as leader, allowed to exist independently under Lithuanian supervision, and then finally absorbed by the Soviet-sponsored Institute of Lithuanian Studies in June 1940. Despite these changes, the YIVO collection remained intact, and was in some respects expanded by the inclusion of books whose owners were fleeing the war. With the launch of Operation Barbarossa in 1941, Nazi forces advanced into Soviet-occupied territory, capturing Vilna—and by extension, the YIVO archives—on 24 June. Shortly thereafter Dr. Johannes Pohl, a representative of the Einsatzstab Reichsleiter Rosenberg (ERR)—the Nazi organisation tasked with stealing or destroying Jewish cultural property—arrived in Vilna to examine the archives. He ordered that Vilna be made a central collection point for the region,