See this reddit thread: https://old.reddit.com/r/history/comments/b6k528/percentage_...
Troops can also desert which is especially prevalent in civil war situations. That's why during war, you need propagandists coming up with constant stories about how horrible and bad the other side is, so that you get people to shoot.
The unit that so brutally killed the tianmen protesters was one of the most brutal ones the Chinese military had. That's why they had to wait for days for it to arrive. Had they deployed different units, they might have fraternized with the protesters and joined them in their protest, making the task even harder for the leadership. Try getting even the most brutal unit to shoot at people in their own uniform.
For military parades, you can't afford 5% of people who intentionally don't march in lock step. That's why usually the troops which participate in such parades are isolated and fed propaganda leading up to the parade.
The human component is a constant variable that needs to be accounted for in military leadership.
What? I've been on countless parades and don't remember any pre-parade propaganda. I've never even heard of such a think in a western military. Parades are just a regular day at the office. Honor guards and flag parties certainly practice heavily, but the idea that anyone "intentionally" doesn't march properly is ... odd.
Also, "lockstep" should not be used in reference to parades. The lockstep was a punishment once inflicted on convicts in an prisons. If you go back hundreds of year there was a style of marching, but it was nothing like the more recent method used as a punishment.
Humans also may be even likelier to be loyal than moral if a drone with a gun follows them around to keep them on-side.
But this is one such check. As I remember it it was at work in the fall of the Soviet Union, and it was worked around at Tiananmen Square (where they brought in troops from the country, not trusting the ones on site to be brutal enough).
I'd be careful about this. There is a general principle in military communities that troops are not to obey "illegal orders" but time and time again throughout history we have seen that backstop fail. At a base level we all do what we think is best for ourselves. Troops will shoot prisoners. Troops will shoot protestors. They will nuke their own hometowns if they believe that is either necessary or if failure to do so will result in their own demise. And many troops, people, will do what they are told out of pure loyalty to a charismatic leader. The only real safeguard is layer upon layer of checks to ensure no one leader can ever exercise independent control.