When I was at the Kennedy School, I taught regularly in an executive program for Army Colonel/Navy Captain level DOD people, including civilians, from all services. Having no personal experience in the military, I was fascinated by the look this afforded into a distinct and proud society. I learned a couple of things that may be relevant to the earlier discussion about military promotions.
First, the various services are really various. For example, the Coast Guard is a lot less military than the Navy, as one might expect. (It used to be called the Jewish Navy when the Navy was, or was believed to be, pervasively anti-Semitic and the CG allowed a lot of Jews with nautical ambitions to follow them; this has to affect culture.)
For another, all the services but one take pains to assure that all officers have direct experience of the core function of that service. All Navy officers serve at sea on ships, and most get to command a craft if only a small one; all Army officers have hauled shoulder arms through the mud and marched and fired various weapons; all Marine officers have climbed out of boats onto beaches and practiced hauling their dead and wounded back out of battles. The exception is the Air Force: it costs a fortune to train a pilot and it appeared that relatively few had ever flown an airplane. As it happens, very few people in the Air Force fly, or even fly in, airplanes except as passengers; most are engaged one way or another in keeping planes fit to fly and fueled up, so it’s actually an organization of parts clerks and mechanics. The personality difference between the typical Air Force colonel and a Marine (for example) in this program was striking. (Full disclosure: I have had the acquaintance of a fair number of Marines and ex-Marines (all male, as it happens) up to the rank of general, and from this happenstance sample I regard that service with real awe: the officers are gentlemen, wise, and gracious, and the leathernecks are competent, creative, dedicated, and it shows.)
Second, by assigning an exercise involving peer evaluation of performance, I once triggered a session of anger and vituperation that really astonished me. Upon inquiry, I learned that I had touched an extremely raw nerve with these folks, occasioned by a promotion system that operates on formal efficiency reports by superior officers. The highest grade is E for excellent (or was then); what made it fearsome was that almost everyone got E for almost everything almost all the time. As a result, every superior had the power to wreck one’s career with a single evaluation below E. At the same time, it was known that so-called “corridor reputation,” the informal, unrecorded, unappealable and unauditable evaluation that attached itself to an officer and circulated through gossip, anecdote, and winks mattered a lot as well. It was explained to me that putting performance evaluation on the table for discussion in this context had opened the door to vent a decade or two of anger and fear for almost everyone in the room.