In 1939, after the invasion of Poland by Nazi Germany and the loss of the defensive war by the Polish army, all the western regions of Poland, including the town of Oświęcim, were annexed by the Third Reich. The town was renamed as Auschwitz and the same name was given to a complex of concentration and extermination camps that were built there. The history of the Auschwitz concentration camp can be divided into two primary periods: the years 1940-1942, when it functioned as a concentration camp and a place of slow extermination, and the years 1942-1944, when it was transformed into the biggest centre of immediate mass extermination of Jews, who had been transported into the camp under the policy conducted by the Third Reich that assumed the extermination of the entire Jewish population in Europe.