Nazi Germany co-formed the "Einsatzgruppe V" in the town, 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, which started World War II. Many Poles expelled from German-occupied Poland were deported to forced labour in the town's vicinity. The Germans also operated a subcamp of the Stutthof concentration camp in the town. On January 30, 1945 in the last months of World War II, the town was captured by the Soviet Red Army. The Red Army established a war hospital in the town for 20,000 people. The town centre was burned and pillaged by Soviet soldiers.