Evidence for the Holocaust comes in four main varieties:[4]
Contemporary documents, including a wide variety of "letters, memos, blueprints, orders, bills, speeches";[6]Holocaust train schedules[4] and statistical summaries generated by the SS;[1] and photographs, including official photographs, clandestine photographs by survivors, aerial photographs, and film footage of the liberation of the camps.[6][7] More than 3,000 tons of records were collected for the Nuremberg trials.[8]
Later testimony from tens of thousands of eyewitnesses, including survivors such as Sonderkommandos, who directly witnessed the extermination process; perpetrators such as Nazi leaders, SS guards, and Nazi concentration camp commandants; and local townspeople.[6][9] Moreover, virtually none of the perpetrators put on trial denied the reality of the systematic murder, with the most common excuse (where one was given) being that they were just following orders.[10]
The perpetrators attempted to avoid creating explicit evidence and they also tried to destroy the documentary and material evidence of their crimes before the German defeat.[4][8] Nevertheless, much of the evidence was preserved and collected by Allied investigators during and after the war, and the overwhelming evidence of the crimes ultimately made such erasure attempts futile. Collectively, the evidence refutes the arguments of Holocaust deniers that the Holocaust did not occur as described in historical scholarship.[8]