Adolf Hitler was an Austrian-born German politician and the leader of the National Socialist German Workers Party, Nazi Party. He was Chancellor of Germany from 1933 to 1945, and head of state from 1934 to 1945.
Hitler encountered the Doctor in 1938 when a Teselecta Justice Vehicle 6019 was attempting to torture the German Leader for his crimes against humanity. The Teselecta Robot was hit by the TARDIS stoping the attack.
When Hitler attempted to shoot the Teselecta he as punched by Rory who then locked him in the Cupboard.
Once he emerged from the cupboard he led Germany into World War II, where German forces and their European allies at one point occupied most of Europe and North Africa. His racially motivated policies resulted in the systematic annihilation of as many as 17 million civilians, including an estimated six million Jews targeted in the Holocaust and between 500,000 and 1,500,000 Roma.