Many Jews in ghettos across eastern Europe tried to organize resistance against the Germans and to arm themselves with smuggled and homemade weapons. Between 1941 and 1943, underground resistance movements formed in about 100 Jewish groups. The most famous attempt by Jews to resist the Germans in armed fighting occurred in the Warsaw ghetto.
In the summer of 1942, about 300,000 Jews were deported from Warsaw to Treblinka. When reports of mass murder in the killing center leaked back to the Warsaw ghetto, a surviving group of mostly young people formed an organization called the Z.O.B. (for the Polish name, Zydowska Organizacja Bojowa, which means Jewish Fighting Organization). The Z.O.B., led by 23-year-old Mordecai Anielewicz, issued a proclamation calling for the Jewish people to resist going to the railroad cars. In January 1943, Warsaw ghetto fighters fired upon German troops as they tried to round up another group of ghetto inhabitants for deportation. Fighters used a small supply of weapons that had been smuggled into the ghetto. After a few days, the troops retreated. This small victory inspired the ghetto fighters to prepare for future resistance.
On April 19, 1943, the Warsaw ghetto uprising began after German troops and police entered the ghetto to deport its surviving inhabitants. Seven hundred and fifty fighters fought the heavily armed and well-trained Germans. The ghetto fighters were able to hold out for nearly a month, but on May 16, 1943, the revolt ended. The Germans had slowly crushed the resistance. Of the more than 56,000 Jews captured, about 7,000 were shot, and the remainder were deported to killing centers or concentration camps.