Nearly six million Jews were murdered in Europe as part of Adolf Hitler's so-called "Final Solution to the Jewish problem".
The decision to kill all the Jews of Europe was formulated in late 1941, and Nazi officials at a meeting in Wannsee near Berlin in January 1942 co-ordinated the apparatus of mass murder.
Most Holocaust victims were murdered in six Nazi extermination camps. Auschwitz-Birkenau in Poland was the largest and at least 1.1 million Jews were killed there. In total 85 per cent of the Jewish population in Poland died - some 2.8 million people.
At least 1.5 million children were killed in the Holocaust. Only an estimated 11 per cent of Jewish children who were alive in 1933 survived the Holocaust.
Other victims of Nazi atrocities - labelled "enemies of the German state" - totalled an estimated 5.5 million and included up to half a million Gypsies, an estimated 10,000-15,000 homosexuals and three million Poles. Catholic and Protestant clergy also were sent to concentration camps as well as Jehovah's Witnesses.
While all countries officially agree with the "never again" lesson of Auschwitz, some Holocaust researchers fault the wartime allies for not bombing the railway tracks that brought Jews from across Europe to the Nazi camp to be killed. Survivors lament what Nobel prize-winning author Elie Wiesel describes as shameful indifference to murder.
The US and Britain garnered much intelligence about the camp during the war, other historians say, but their priority was the total military defeat of Nazi Germany, not the rescue of the Jews.