Many of the remaining Jews in the Warsaw Ghetto decided to fight, and many were helped by the Polish underground. The Jewish Combat Organization (ŻOB, ) was formed in October 1942 and tasked with resisting any future deportations. It was led by 24 year–old Mordechai Anielewicz. Meanwhile, the Polish Home Army, Armia Krajowa (AK), began to smuggle weapons, ammunition and supplies into the Ghetto for the uprising. Von Sammern-Frankenegg was relieved of duty by Heinrich Himmler on April 17, 1943 and replaced with SS- und Polizeiführer Jürgen Stroop. Stroop took over from von Sammern-Frankenegg because of his unsuccessful offensive against the Ghetto underground.