Holocaust

The Holocaust was the industrialised genocide of the Jews and others considered "undesirable" by the Nazi Party during World War II. (PROSE: Timewyrm: Exodus)

Grigori Rasputin planned to prevent the Holocaust after receiving a vision of the future, but the First Doctor removed his knowledge of it. (AUDIO: The Wanderer)

The Seventh Doctor listed the Holocaust as one of the terrible things that happened after he set history back on track by freeing the Timewyrm from Adolf Hitler's mind. (PROSE: Timewyrm: Exodus)

When, in an alternate timeline, the British government began rounding up immigrants and sending them to "labour camps", Wilfred Mott compared the situation to the Holocaust. (TV: Turn Left)