On September 27, 1939 Bischoff and his "Einsatzkommando" led a raid on the town of Pułtusk, which ended with the mass-expulsion of the town's large Jewish population and their deportation across the Narew River into the Soviet-occupied east. "Einsatzgruppe IV" was also involved in the round-up of Warsaw's Jewish inhabitants, setting in motion their eventual ghettoization. "Einsatzgruppe IV" was formally disbanded on November 20, 1939. Its officers and men were stationed in the Polish General Government and converted into stationary units of the "Sicherheitspolizei" (security police) in Warsaw, under the command of "SS-Standartenführer" Josef Albert Meisinger.