Well, it doesn't all happen on one day. It creeps up on people by degrees, and they may wake up one morning (as a lot of German soldiers, officers, and civilians did, each in his or her own time) and realize with horror that they are irrevocably trapped in a corrupt national system, and it's too late now for them to undo what has been done or to escape it...or they may not wake up to that at all, in which case they will continue serving blindly right to the end, and believing blindly that what they are doing is not only right, not only good, it is the only thing that can be done.

Those who do wake up to the ugly reality tend to lose their enthusiasm, lose their fighting spirit, and they are castigated for it...shamed publicly...called "defeatists", "appeasers", "cowards", "weaklings", "failures", even "traitors". Some will be demoted. Some disciplined. A few executed.

The true believers who go on to the end are hunted by the victors after it's over and called "war criminals" (and some of them were just that, while some were not).

It could happen in any country, depending on the ruthlessness and cunning of its leaders, and depending on the time and general circumstances.