Reichsgau Wartheland in the context of "Population transfer"

Chełmno, or Kulmhof, was the first of Nazi Germany's extermination camps and was situated 50 km (31 mi) north of Łódź, near the village of Chełmno nad Nerem. Following the invasion of Poland in 1939, Germany annexed the area into the new territory of Reichsgau Wartheland. The camp, which was specifically intended for no other purpose than mass murder, operated from December 8, 1941, to April 11, 1943, parallel to Operation Reinhard during the deadliest phase of the Holocaust, and again from June 23, 1944, to January 18, 1945, during the Soviet counter-offensive. In 1943, modifications were made to the camp's killing methods as the reception building had already been dismantled.

At the very minimum, 152,000 people were murdered in the camp, which would make it the fifth deadliest extermination camp, after Auschwitz, Treblinka, Bełżec, and Sobibór. However, the West German prosecution, citing Nazi figures during the Chełmno trials of 1962–65, laid charges for at least 180,000 victims. The Polish official estimates, in the early postwar period, have suggested much higher numbers, up to a total of 340,000 men, women, and children. The Kulmhof Museum of Martyrdom [pl] gives the figure of around 200,000, the vast majority of whom were Jews of west-central Poland, along with Romani people from the region, as well as foreign Jews from Hungary, Bohemia and Moravia, Germany, Luxembourg, and Austria transported to Chełmno via the Łódź Ghetto, on top of the Soviet prisoners of war. The victims were murdered using gas vans. Chełmno was a place of early experimentation in the development of the Nazi extermination programme.

Following the Invasion of Poland at the beginning of World War II, nearly a quarter of the entire territory of the Second Polish Republic was annexed by Nazi Germany and placed directly under the German civil administration. The rest of Nazi-occupied Poland was renamed as the General Government district. The annexation was part of the "fourth partition of Poland" by Nazi Germany and the Soviet Union, outlined months before the invasion, in the Molotov–Ribbentrop Pact.

Some smaller territories were incorporated directly into the existing Gaue East Prussia and Silesia, while the bulk of the land was used to create new Reichsgaue Danzig-West Prussia and Wartheland. Of those, Reichsgau Wartheland was the largest and the only one comprising solely the annexed territory.

The Łódź Ghetto, or Litzmannstadt Ghetto (after the Nazi German name for Łódź), was a Nazi ghetto established by the German authorities for Polish Jews and Roma following the Invasion of Poland. It was the second-largest ghetto in all of German-occupied Europe after the Warsaw Ghetto. Situated in the city of Łódź, and originally intended as a preliminary step upon a more extensive plan of creating the Judenfrei province of Warthegau, the ghetto was transformed into a major industrial centre, manufacturing war supplies for Nazi Germany and especially for the Wehrmacht. The number of people incarcerated in it was increased further by the Jews deported from Nazi-controlled territories.

On 30 April 1940, when the gates closed on the ghetto, it housed 163,777 residents. Because of its remarkable productivity, the ghetto managed to survive until August 1944. In the first two years, it absorbed almost 20,000 Jews from liquidated ghettos in nearby Polish towns and villages, as well as 20,000 more from the rest of German-occupied Europe. After the wave of deportations to Chełmno extermination camp beginning in early 1942, and in spite of a stark reversal of fortune, the Germans persisted in eradicating the ghetto: they transported the remaining population to Auschwitz and Chełmno extermination camps, where most were murdered upon arrival. It was the last ghetto in occupied Poland to be liquidated. A total of 210,000 Jews passed through it; but only 877 remained hidden when the Soviets arrived. About 10,000 Jewish residents of Łódź, who used to live there before the invasion of Poland, survived the Holocaust elsewhere.