In his 1965 essay "Command and Compliance", which originated in his work as an expert witness for the prosecution at the Frankfurt Auschwitz Trials, the German historian Hans Buchheim wrote there was no coercion to murder Jews and others, and all who committed such actions did so out of free will. Buchheim wrote that chances to avoid executing criminal orders "were both more numerous and more real than those concerned are generally prepared to admit", and that he found no evidence that SS men who refused to carry out criminal orders were sent to concentration camps or executed. Moreover, SS rules prohibited acts of gratuitous sadism, as Himmler wished for his men to remain "decent"; acts of sadism were carried out on the initiative of those who were either especially cruel or wished to prove themselves ardent National Socialists. Finally, he argued that those of a non-criminal bent who committed crimes did so because they wished to conform to the values of the group they had joined and were afraid of being branded "weak" by their colleagues if they refused.
Use of armoured forces was crucial for both sides on the Eastern Front. Operation Barbarossa, the German invasion of the Soviet Union in 1941, involved a number of breakthroughs and encirclements by motorised forces. Its goal according to Führer Directive 21 (18 December 1940) was "to destroy the Russian forces deployed in the West and to prevent their escape into the wide-open spaces of Russia." The Red Army was to be destroyed west of the Dvina and Dnieper rivers, which were about 500 kilometres (310 mi) east of the Soviet border, to be followed by a mopping-up operation. The surprise attack resulted in the near annihilation of the Voyenno-Vozdushnye Sily (VVS, Soviet Air Force) by simultaneous attacks on airfields, allowing the Luftwaffe to achieve total air supremacy over all the battlefields within the first week. On the ground, four German panzer groups outflanked and encircled disorganised Red Army units, while the marching infantry completed the encirclements and defeated the trapped forces. In late July, after 2nd Panzer Group (commanded by Guderian) captured the watersheds of the Dvina and Dnieper rivers near Smolensk, the panzers had to defend the encirclement, because the marching infantry divisions were still hundreds of kilometres to the west.
"The persecution of Jews in occupied Poland meant that we could see horror emerging gradually in many ways. In 1939, they were forced to wear Jewish stars, and people were herded and shut up into ghettos. Then, in the years '41 and '42 there was plenty of public evidence of pure sadism. With people behaving like pigs, I felt the Jews were being destroyed. I had to help them. There was no choice."
After 1942, the economic functions of the camps, previously secondary to their penal and terror functions, came to the fore. Forced labor of camp prisoners became commonplace. The guards became much more brutal, and the death rate increased as the guards not only beat and starved prisoners, but killed them more frequently. Vernichtung durch Arbeit ("extermination through labor") was a policy—camp inmates would literally be worked to death, or to physical exhaustion, at which point they would be gassed or shot. The Germans estimated the average prisoner's lifespan in a concentration camp at three months, due to lack of food and clothing, constant epidemics, and frequent punishments for the most minor transgressions. The shifts were long and often involved exposure to dangerous materials.
The first “bunker,” with two sealed rooms, operated from January 1942 to the end of that year. The second, with four air tight rooms, became redundant in the spring of 1943, but remained standing and was used again in the autumn of 1944 when extra “capacity” was needed for the murder of Hungarian Jews and the liquidation of the ghettos. The second measured about 1.134 square feet. The victims murdered in the “bunkers” were first obliged to undress in temporary wooden barracks erected nearby. Their bodies were taken out of the gas chambers and pushed to pits where they were burned in the open.