20% is unrealistically high.Zach, I think more highly of the US military than a lot of people you're arguing with, but even so 99.9+% is unrealistic. A lot more people will do as they're told than you might think.
Practically speaking, I'd expect at least 20% will follow orders due to a lack of consciense, courage, or both. For militaries in most other nations, I'd expect a much higher proportion than that.
Mine Kay be too low, but it is definitely not substantial enough when you include those that are willing to make sure it doesn't happen, and the amount of friendly fire that would happen.
One also has to take into account current US Military ROE. Unless fire upon they will not fire back.
The Army and Marines are the only branch worthwhile for this kinda thing anyway.
AF and Navy don't have large enough ground combatants to mobilize, and one has to take into account how stupid it would be to throw everyone out onto infantry line in any branch. Because that is how you get people to scared to act, give up when shot at. Etc etc.
Because they are back fighting force.
Taking into count Infantry and other Combat oriented MOSs it would be below 5%, and that is pushing it of the combat arms alone