In August 1939, the summer camp was closed and the Wehrmacht impounded the area. In November 1939, it became the POW camp "Stalag IX-B", housing prisoners from at least eight countries: France, the Soviet Union, Italy, Great Britain, Belgium, Serbia, Slovakia and the US. The inmates were used as forced labourers in agriculture, forestry and in industry at Gelnhausen, Wächtersbach, Hanau, Offenbach and Frankfurt. There are no data on the number of dead. The first figures on the number of inmates date to September 1941, when the Wehrmacht notified the IRC of 18,483 POWs. After December 1941, Soviet prisoners were first mentioned. The number of prisoners peaked in September 1944 at 25,640 (12,537 French, 11 British, 704 Serbs and Slovaks, 8,448 Soviets and 3,941 Italians). At that point there was severe overcrowding. Inmates later said that around Christmas 1941 about 20 Soviets died each day from hunger and exhaustion. From 5 December 1941 to 22 January 1942, 356 Soviet prisoners died, before the authorities stopped issuing certificates of death. Soviet prisoners were not provided any shelter, given less and worse food than other prisoners, and forced to do hard labour such as quarrying.