Nazi Germany co-formed the "Einsatzgruppe V" in the city, which then entered several Polish cities and towns, including Grudziądz, Mława, Ciechanów, Łomża and Siedlce, to commit various atrocities against Poles during the German invasion of Poland that began World War II in 1939. German troops invaded Poland also from Olsztyn. After the German invasion of Poland, local Poles were also subjected to mass executions and deportations to occupied Poland. Arrested Poles were held in a local prison and then forced to remove Polish signs and inscriptions in the city, while the German population gathered and insulted them. The "Gazeta Olsztyńska" was abolished by the German authorities, the newspaper's headquarters was demolished and the editor-in-chief Seweryn Pieniężny was arrested and executed in the along with co-publisher Wojciech Gałęziewski and the "Rolnik" Cooperative chief Leon Włodarczyk, while Pieniężny's wife was deported to the Ravensbrück concentration camp. The last pre-war Polish consul in Allenstein, Bohdan Jałowiecki, along with the consulate staff, was imprisoned in the Hohenbruch and Soldau concentration camps, and then murdered. Polish teachers were deported to the Dachau concentration camp.