The Warsaw Ghetto Uprising was the 1943 act of Jewish resistance in the Warsaw Ghetto in German-occupied Poland during World War II to oppose Nazi Germany's final effort to transport the remaining ghetto population to Majdanek and Treblinka. After the Grossaktion Warsaw of summer 1942, in which more than a quarter of a million Jews were deported from the ghetto to Treblinka and murdered, the remaining Jews began to build bunkers and smuggle weapons and explosives into the ghetto. The left-wing Jewish Combat Organization (ŻOB) and right-wing Jewish Military Union formed and began to train, despite the lack of support from the better-armed and -equipped Polish resistance groups. A small resistance effort to another roundup in January 1943 was partially successful and spurred the Polish groups to support the Jews in earnest.