Towards the end of World War II in 1944, as Britain and the United States approached the concentration camps from the west, the Soviet Union was advancing from the east. Trapped in the middle of the allied advance, the SS, not wanting the world to know about the Holocaust, decided to abandon the camps, moving or destroying evidence of the various atrocities they had committed there. Thousands of prisoners were killed in the camps before the marches commenced, in acts which at Nuremberg were tried as crimes against humanity.