I have to wonder at the US military- did they just have to accept they had to go into war with no defined ‘success’ criteria, no clear method to work towards an acceptable outcome, no idea what the CinC expects or wants - or is this not uncommon and they make their own decisions on what to do/aim towards?
This passage from Tennysons' 'Charge of the Light Brigade' comes to mind:
“Forward, the Light Brigade!”
Was there a man dismayed?
Not though the soldier knew
Someone had blundered.
Theirs not to make reply,
Theirs not to reason why,
Theirs but to do and die.
Into the valley of Death
Rode the six hundred.
And there you pretty much have it. Military personnel (and not just the US's) simply go where they are sent and do what they are told because that is what they are trained to do.
In the US they are told that they do not have to obey 'unlawful orders'. In the case of your CO telling you to shoot an innocent civilian who poses no danger it's pretty clear that that's an illegal order. But it's a pretty grey area when it comes to things like being sent to 'wage war'. The same grey area that's allowing Scrotus to do what he's doing.
It would take a mass mutiny or mass desertion of 100s of 1000s of personnel, high and low, to possibly change what's going on. Or the Joint Chiefs of Staff to start refusing his commands, but I don't see that happening either.