Concentration Camps where used to to keep Jews to be killed, or labor, if not old enough. Some of the Jews had endure this and more during the holocaust, despite the terrible circumstances
The death march was a walk, that alone (was a Genocide) had killed hundreds, if not thousands of Jews. This was only one of many atrocities.
The Nazi were the ones who had done this, and started WWII sometime later. They had followed their leader Hitler
The picture here is Hitler himself. The leader of the Nazi.