A gas van or gas wagon was a truck re-equipped as a mobile gas chamber. During World War II and the Holocaust, Nazi Germany developed and used gas vans on a large scale to kill inmates of asylums, Poles, Romani people, Jews, and prisoners in occupied Poland, Belarus, Nedić's Serbia, the Soviet Union, and other regions of German-occupied Europe. There are several documented cases of gas vans used by Soviet NKVD during the Great Purge.