This is a picture of a memorial in Berlin Mitte, where from 1942 onwards the Nazis brought together 55.000 Jewish men, women, and children. They were then put on transport to Auschwitz and Theresienstadt, where they would be brutally murdered. The details on the memorial are pretty effective in reminding us of the scope of the inhumanity that the Nazis brought over Europe, but in the end the message is so simple that even Donald Trump must be able to understand this:

Never forget — resist war — protect peace.