As the invasion began, the Germans pursued the fleeing Red Army, leaving a security vacuum. Reports surfaced of Soviet guerrilla activity in the area, with local Jews immediately suspected of collaboration. Heydrich ordered his officers to incite anti-Jewish pogroms in the newly occupied territories. Pogroms, some of which were orchestrated by the "Einsatzgruppen", broke out in Latvia, Lithuania, and Ukraine. Within the first few weeks of Operation Barbarossa, 40 pogroms led to the deaths of 10,000 Jews, and by the end of 1941 some 60 pogroms had taken place, claiming as many as 24,000 victims. However, SS-"Brigadeführer" Franz Walter Stahlecker, commander of "Einsatzgruppe" A, reported to his superiors in mid-October that the residents of Kaunas were not spontaneously starting pogroms, and secret assistance by the Germans was required. A similar reticence was noted by "Einsatzgruppe" B in Russia and Belarus and "Einsatzgruppe" C in Ukraine; the further east the "Einsatzgruppen" travelled, the less likely the residents were to be prompted into killing their Jewish neighbours.