In this mad, fevered time, when people are starting to ask about a possible Trump coup, in "he wouldn't, would he?" terms, it's notable that he's appointed new civilian heads at the DoD. The "no, he couldn't possibly" argument is that generals would never agree to take part in a military coup.

But can the Defense Secretary fire those generals and replace them with others, who would theoretically be more pliant?

In this highly controversial time, some Democrats are suggsting that Trump might use the power the military to retain power, and that this would constitute a military coup, and that Trump's appointment of new civilian leaders of the Pentagon is a staging post on the road to this.

Some people suggest that this wouldn't be possible, because civilian leaders can't just issue any order to military generals and expect it to be complied with.

My question is, can the DoD officials simply sack the generals and replace them with other generals who would be more co-operative? Or is there a more complex process than this?