Abraham Gancwajch

In the Warsaw Ghetto Gancwajch lived a lavish life, collecting hefty sums from others by various means. On the other hand, he helped the poor and artists. But all his initiatives became corrupted; for example, he set up a hospital with ambulances, but the network soon came to be used primarily for smuggling by Group 13, a racketeering network that was officially to have combated black-marketeering in the Ghetto. After most of the Group 13 was eliminated by the Germans in 1943, Gancwajch reemerged outside the ghetto on the Aryan side in Warsaw, where he and other members of his group, pretending to be Jewish underground fighters, were hunting for Poles hiding or otherwise supporting the Jews. He was also the leader of the infamous Żagiew, a Gestapo-sponsored Jewish organization. He is also known to have tried to sabotage attempts at the Warsaw Ghetto Uprising. The Jewish Combat Organization sentenced him to death, but were never able to execute him. His ultimate fate remains unknown.

After the German invasion of Poland, he surfaced in Warsaw as a refugee from Łódź, and as a person with connections to the German Sicherheitsdienst (SD). He first became a Nazi collaborator as a leader of the Hashomer Hatzair, delivering weekly intelligence reports to the Germans. In December 1940 he founded the Group 13 network, a Jewish Nazi collaborationist organization in the Warsaw Ghetto, described by Israel Gutman and Emanuel Ringelblum as the "Jewish Gestapo".

Gancwajch was born in Częstochowa, Poland. As a youth, he apprenticed as a journalist and editor in Łódź, and eventually left Poland for Vienna, Austria, where he worked as a reporter on Jewish affairs for the Gerechtigkeit (Justice) periodical edited by Irena Harand. He was expelled from Vienna around 1936–1938 and returned to Poland, having gained his reputation as a teacher and a Zionist journalist with an oratorical skill.

Abraham Gancwajch (1902–1943) was a prominent Nazi collaborator in the Warsaw Ghetto during the World War II occupation of Poland, and a Jewish kingpin of the ghetto underworld. Opinions about his ghetto activities are controversial, though modern research concludes unanimously that he was an informer and collaborator motivated chiefly by personal interest.