In mid-August of 1941, members of the mobile killing unit Einsatzgruppe C of the chief of the Security Police and the SD (Security Service) murdered the Jewish population in the town of Belaya Tserkov, south of Kiev. Ninety Jewish children who were also supposed to be shot were initially locked in a building. Helmuth Groscurth, a Wehrmacht officer, heard about this and tried to save them. A year earlier he had already reported to members of the Wehrmacht on the Western Front about mass murders committed by the mobile killing units in Poland. Now he intervened by informing his superior in the Army High Command 6, which then postponed the shooting. A short time later, however, the commander in chief of the 6th Army, Walther von Reichenau, approved the continuation of the murderous operation. On August 22, 1941, all of the children were murdered. In February 1943, Groscurth was taken prisoner of war; he died two months later of typhus in a Soviet prisoner-of-war camp.

In January of 1942, Szlama Winer was deported to the Chelmno (Kulmhof) extermination camp, where he was forced to bury the Jews killed in gas vans. He managed to escape. Winer then became one of the first to report in detail on the German mass murders. His eyewitness report was added to the secret Jewish underground archive of the Warsaw Ghetto. The evidence collected there was to serve after the war to investigate and punish the crimes. The archivists also sent the report to the Polish exile government in London. Nevertheless, this and other reports failed to move Britain and the Allied countries to take action against the genocide. They instead concentrated more on defeating the German Reich militarily. Szlama Winer was caught a short time later and murdered in Belzec extermination camp.

In late September of 1942, the Jewish resistance organization Comité de Défense des Juifs (CDJ) in Belgium successfully prevented the deportation of Jews from Charleroi. CDJ member Max Katz convinced Jules Mehlwurm to work with the group. As the local leader of the mandatory association of Jews in Belgium, Mehlwurm was supposed to help organize the deportations. Katz persuaded Mehlwurm to give the German security police a list of names with false addresses for the imminent deportation. Because the police were looking for the Jews at these other locations, the resistance group was able to warn more than one thousand Jews. All of them except for 27 were able to flee to prepared hiding places. The group looked after the needs of the Jews in their hiding places. As of February 1943, the CDJ of Charleroi published an underground newspaper in which it informed those in hiding of dangers and called upon them to resist.