So meritocracy is against obtaining rank for any other reason other than merit, right?
It will be foreign troops ready/sent to take over the US military.
That was the idea. West Point and the Naval Academy were supposed to make that happen. Now against fulfillment of the intent is the fact that the most senior officers are nominated by the President and have to be confirmed by Congress. By WW II you see politics creeping in with guys like McArthur compared to those holding to traditional values like Marshall and Eisenhower.