"Between July 22 and September 12, 1942, the German authorities deported or murdered around 300,000 Jews in the Warsaw ghetto. SS and police units deported 265,000 Jews to theTreblinka killing center and 11,580 to forced-labor camps. The Germans and their auxiliaries murdered more than 10,000 Jews in the Warsaw ghetto during the deportation operations. The German authorities granted only 35,000 Jews permission to remain in the ghetto, while more than 20,000 Jews remained in the ghetto in hiding. For the at least 55,000-60,000 Jews remaining in the Warsaw ghetto,deportation seemed inevitable.
In response to the deportations, on July 28, 1942, several Jewish underground organizations created an armed self-defense unit known as the Jewish Combat Organization(Zydowska Organizacja Bojowa; ZOB). Rough estimates put the size of the ZOB at its formation at around 200 members. The Revisionist Party (right-wing Zionists known as the Betar) formed another resistance organization, the Jewish Military Union (Zydowski Zwiazek Wojskowy; ZZW). Although initially there was tension between the ZOB and the ZZW, both groups decided to work together to oppose German attempts to destroy the ghetto. At the time of the uprising, the ZOB had about 500 fighters in its ranks and the ZZW had about 250. While efforts to establish contact with the Polish military underground movement (Armia Krajowa, or Home Army) did not succeed during the summer of 1942, the ZOB established contact with the Home Army in October, and obtained a small number of weapons, mostly pistols and explosives, from Home Army contacts.”