The UK's Holocaust Memorial Day commemorations have been launched with a concert in Cardiff attended by around 100 genocide survivors and rescuers.
Prime Minister Tony Blair joined them at the Wales Millennium Centre event to remember victims of genocides.
This year's theme pays tribute to those who played a part in rescuing victims.
Former UN general Romeo Dallaire, speaking about his mission in Rwanda, was applauded after saying: "We called it genocide, and no-one came."
The events commemorate the 61st anniversary of the liberation of the Nazi death camp Auschwitz-Birkenau.
Thursday's concert, which featured music, poetry and dance, marked the first time Wales has led the UK's annual commemoration.
Eva Clarke, who was born at Mauthausen camp in Austria, in April 1945, introduced the concert with a tribute to survivors like her mother, Anna Bergman, 88, as well as the rescuers who "threw a lifeline to humanity" with life-saving acts of bravery.
Among those honoured was American Charles Fawcett for his work in Marseille with Varian Fry during World War II.
They rescued hundreds of Jewish artists, writers, scientists and their families.
Mr Fawcett took to the stage in a wheelchair as a film about him was shown in which he said: "I thought we could make a difference. It's a responsibility people have."
General Dallaire, who wrote Shake Hands with the Devil, about the UN mission to Rwanda during the 1994 genocide, was the most challenging speaker of the evening.
He pointed to the delays in reinforcing his UN mission at the time and said: "We do not have the right to assess and establish a priority for humanity.
"Are all humans human or are some more human than others? Do some count more than others?"
Mr Blair pointed out that the Nazis made Jews in war-torn Europe suffer in the Holocaust "precisely because they were a people".
The commemoration fell on the eve of Holocaust Memorial Day
"We recognise that for all its force, it was not strong enough to overcome them, those who made the difference."
He added: "It happened and in the lifetime of my father it happened".
As he finished, by saying that we should never "at any time let it happen again", he was heckled briefly by a man who had earlier been in the foyer lobbying for the killing of Armenians in Turkey during World War I to be recognised as genocide.
The man left the auditorium voluntarily after disapproving murmurs and "shush" noises from the audience.
Welsh First Minister Rhodri Morgan and Cardiff Council leader Rodney Berman told the audience that, earlier on Thursday, every school child in Wales had taken a pledge to "make a difference".
The pledge was in the form of repeating a specially commissioned poem written by Gwyneth Lewis, Wales' national poet.
Chief Rabbi Jonathan Sacks told the packed auditorium that the notion of changing the world by changing a life was "the only way the world can be changed".
The concert ended with the lighting of the memorial flame by seven-year-old Samuel Pfister, the great-grandson of Belgian woman Claire Keen-Thyrin, who was a teenager when she helped hide Jewish children on the run from the Nazis.
The Wales Millennium Centre evening took account of the Jewish Sabbath, as this year's Holocaust Memorial Day falls on a Friday, the first time since the event was instituted.