In the decades since its liberation, Auschwitz has become a primary symbol of the Holocaust. Historian Timothy D. Snyder attributes this to the camp's high death toll and "unusual combination of an industrial camp complex and a killing facility", which left behind far more witnesses than single-purpose killing facilities such as Chełmno or Treblinka. In 2005 the United Nations General Assembly designated 27 January, the date of the camp's liberation, as International Holocaust Remembrance Day. Helmut Schmidt visited the site in November 1977, the first West German chancellor to do so, followed by his successor, Helmut Kohl, in November 1989. In a statement on the 50th anniversary of the liberation, Kohl said that "darkest and most awful chapter in German history was written at Auschwitz." In January 2020, world leaders gathered at Yad Vashem in Jerusalem to commemorate the 75th anniversary. It was the city's largest-ever political gathering, with over 45 heads of state and world leaders, including royalty. At Auschwitz itself, Reuven Rivlin and Andrzej Duda, the presidents of Israel and Poland, laid wreaths.