Hitler, Volume II, Chapter XV of Mein Kampf: 

• If at the beginning of the War and during the War, 12 or 15 thousand of these Hebrew corrupters of the people had been held under poison gas, as happened to hundreds of thousands of our very best German workers in the field, the sacrifice of millions at the front would not have been in vain.

Just as German soldiers had been "held under poison gas" in the First World War, so Jews would be "held under poison gas" in the Holocaust. 

The Holocaust repeated the trauma of the First World War: Jews suffered the fate of German soldiers.

Do unto the others as had been done unto you.