When the final survivors of World War II are soon gone, the world will lose living testimony of a fight against tyranny that once involved millions of people and unimaginable pain and destruction. That will usher in a dangerous period when malevolent political actors will find it easier to distort history to bolster their own power. This has already been happening as the lessons of the Nazi Holocaust, from which there are dwindling numbers of survivors to bear witness, have been challenged by a rise in antisemitism in Western societies.