Hitler had been in control of Germany for six years when World War II began, and in that time had worked hard to create a formidable army, breaking many of the stipulations of the Treaty of Versailles. The establishment of the Hitler Youth essentially acted as a training programme for young men and women in Germany, moulding them into the adults who would serve in the Wehrmacht (the German Army). These adults had been taught from a very young age the principles of Nazism, and Hitler’s nationalist ideals had been embedded into their collective psyche. As such, Hitler created an army which was fundamentally an extension of his own desires.
The average German soldier was a graduate of the Hitler Youth, participation in which was compulsory after 1936. They would have been taught that Germans belonged to a superior race of human, and the German soldiers believed this to varying degrees. A significant portion were likely to have believed this, having been brought up in the volatile environment of inter-war Germany, suffering the incompetent left-wing leaders and financial difficulties of the Weimar Republic; by comparison, Hitler was the answer to all problems, and so his word was taken as gospel.
Many German soldiers will have understood that Hitler was one of the most charismatic and persuasive leaders in recent history, and that he was a strong contender in the battle for domination. These men and women may have fought simply to protect themselves, but may not have wholly bought into the ideals of the Nazi regime. Some such people were behind the July 1944 assassination effort, leading the attempted military coup from within the Wehrmacht.
Roughly 20 million persons were active in the German Army at various points in World War Two. The Wehrmacht was a particularly well-oiled machine; the 1936-1939 Spanish Civil War allowed Hitler time to try out his new army, the Condor Legion , and refine any issues that were apparent. Conscription was introduced in Germany as early as 1935, meaning that conscript German soldiers had significantly more time to prepare and train for warfare than British or American conscripts.
The Wehrmacht had a particular edge of the British and American armies in that soldiers underwent thorough examinations to determine which posting would suit their capabilities best, meaning that each division of the armed forces was made up by the people who could perform the best. Neither the British or American armies did this, meaning that strengths were not utilised as well as in the Wehrmacht, and contributed to the overwhelming successes that the Axis forces enjoyed early in the war.