Why are so many high ranking officers being fired by our current administration? Is it because they won't back the POTUS?

I have read many articles lately that point to a sinister agenda to impose martial law and render the Constitution meaningless.  Some articles present a valid rationale for the Obama Administration firing admirals and generals who oppose firing or ordering their troops to fire on American citizens if the need arose.  Add to these articles all the abuses by this administration and it gives one pause to wonder if there is something on the horizon we the people should worry about.