Survivors of the Nazi's notorious Auschwitz death camp are taking center stage at the memorial service to mark 80 years since its liberation by Soviet troops.

The 80th anniversary of the liberation of Auschwitz was widely acknowledged Monday as the last major observance that any notable number of survivors will be able to attend.

As world leaders gather at Auschwitz to mark a solemn anniversary, one notable figure will be missing, sparking intrigue and speculation across the globe.