ŻZW
Preparations to resist had been going on since the previous autumn. The first instance of Jewish armed struggle in Warsaw had begun. The underground fighters from ŻOB (: Jewish Combat Organization) and ŻZW (: Jewish Military Union) achieved considerable success initially, taking control of the Ghetto. They then barricaded themselves in the bunkers and built dozens of fighting posts, stopping the expulsions. Taking further steps, a number of Jewish collaborators from Żagiew were also executed. An offensive against the Ghetto underground launched by Von Sammern-Frankenegg was unsuccessful. He was relieved of duty by Heinrich Himmler on April 17, 1943 and court-martialed.