The Group Thirteen network (Polish: Trzynastka, Yiddish: דאָס דרײַצענטל) was a Jewish German organization in the Warsaw Ghetto during the German occupation of Poland in World War II. The Thirteen took its informal name from the address of its main office at 13 Leszno Street in Warsaw.

The group was founded in December 1940 and led by Abraham Gancwajch the former head of Hashomer Hatzair in Łódź. Sanctioned by Sicherheitsdienst (SD), and also known as the Jewish Gestapo, the unit reported directly to the German Gestapo office. 

The group vied for control of the ghetto with the Judenrat and infiltrated the Jewish opposition within the ghetto  The group's most important branch was the Office to Combat Usury and Profiteering in the Jewish Quarter of Warsaw. Supposed to fight the black market, it actually collected large sums via racketeering, blackmail, and extortions. 

The group also ran its own prison. In total, the group numbered between three and four hundred uniformed Jewish officers, distinguished by caps with green bands. There was actually an admittance payment to become a member of the deviant  "13" was several thousand zlotys issued by the German-controlled Bank. 

In July 1941 the Group 13 lost to the Judenrat in the political arena and the Office was incorporated into the Jupo police force. 

After the Office was closed, the active members of the Group 13 centered on Gancwajch, and concentrated their efforts on setting up their own infirmary and ambulance service (the so-called Emergency Service, or the First Aid Station, which was created in May 1941). However, the company's resources soon became used predominantly for smuggling and contraband. They also ran other operations, for example, a brothel at the Britannica hotel. They had near-total control over the horse-drawn carriages and all transportation within the ghetto. 

Leadership Split

In mid-1941, shortly before the Office was closed, there was a split in the Group leadership when Morris Kohn and Zelig Heller broke with Gancwajch and established their own organizations.[4] Kohn and Heller eventually outlasted the Group. Their demise only came during the mass deportations of Jews from the Warsaw ghetto to the German Treblinka extermination camp by Germans in the course of Grossaktion Warsaw. 

The rise and fall of the Group was likely related to the struggles for power between various factions in the German military staff and bureaucracy who supported various factions in the Ghetto for their own financial benefits. 

In April 1942 many members of the Group 13 were executed by Germans in Operation Reinhard during which Germans killed around 2 million Polish Jews.  Gancwajch and surviving members of the group later re-emerged posing as Jewish underground fighters, though in reality they were hunting and murdering Poles hiding or otherwise supporting the Jews. 

After closing the Jewish Gestapo, Gancwajch stayed in Warsaw outside the ghetto, where he continued working for the Germans. He was rumored to have died around 1943; a hypothesis about his post-war collaboration with the NKVD was never confirmed.

W. D. Rubinstein, The Left, the Right, and the Jews Universe Books, 1982, ISBN 0-87663-400-5, (Google Print)