The prisoners in the POW camp in Żyrardów, captured after the Battle of the Bzura, were denied any food and starved for ten days. In many cases Polish POWs were burned alive. Units of the Polish 7th Infantry Division were massacred after being captured in several individual acts of revenge for their resistance in combat. On September 11, "Wehrmacht" soldiers threw hand grenades into a school building where they kept Polish POWs. According to German historian Jochen Böhler, the Wehrmacht mass murdered at least 3,000 Polish POWs during the campaign.