Stroop was involved in the suppression of the Warsaw Ghetto Uprising, an action which cost the lives of over 50,000 people. He was sent to Warsaw on 17 April 1943 by Heinrich Himmler, as a replacement for SS-Oberführer Ferdinand von Sammern-Frankenegg, who was relieved of duty.[17][18] Stroop took over from Sammern-Frankenegg following the latter's failure to suppress the uprising at the onset.[19] He commented to war crimes investigators: