Final answer:
To mitigate psychological damage to their soldiers, the Nazis transitioned from shootings by the Einsatzgruppen to using gas vans and eventually established extermination camps with gas chambers.
Step-by-step explanation:
Efforts to Prevent Psychological Damage among Nazi Killing Units
The Nazis implemented several measures to protect their soldiers from psychological damage incurred by carrying out mass executions. Initially, the Einsatzgruppen, mobile killing units, conducted mass shootings of Jewish communities and political opponents. To reduce the psychological burden placed on these soldiers, the Nazis introduced gas vans as an alternative to shooting; these vans used carbon monoxide to murder the victims. However, the continued psychological toll led to the creation of extermination camps where mass murder could occur on an even greater scale, utilizing the poison gas Zyklon B in gas chambers. These camps included infamous names such as Auschwitz-Birkenau and Majdanek. The use of euphemistic language like the 'Final Solution' to refer to the murdering of Jewish people was part of the Nazis' approach to disguise the brutal reality of their actions.
Furthermore, as the mass shootings were causing mental breakdowns among German soldiers, the Nazis increasingly relied on local collaborators from the occupied regions, known as 'Hiwis', and also involved regular units of the Wehrmacht and the Waffen SS. The Chelmno killing center was the first of its kind established solely for the purpose of mass execution, and several others followed in occupied Poland. These steps formed part of a systematic approach to what would ultimately be referred to as the Holocaust.