I recall a statement by a senior officer (not German, but likely known by name by most readers) about his experience on a civilian university.
He recounted that after being in uniform and equipped with the authority of a superior in the army and equipped with a degree from a military college he had a culture shock when he joined the civilian university.
Suddenly, his authority was gone and even much younger guys and gals were beating him in many regards - especially discussions. He had to adapt and become better, develop himself, to cope with this more challenging environment.
This is but one of many anecdotes about the poor effect of authoritarian organisations on the intellectual development. You don't need to have good arguments or even be correct if you can simply give orders to have it your way. Having good arguments doesn't serve you well in disagreements with your superior if he can simply order you to do it his way.
Well, how could this be addressed without forcing military personnel into a civilian environment for years? After all, you'll only know who of them will become senior personnel with a real need for intellectual skills after a couple of years, and few will cope well with a university environment after the age of 30 anyway.
This problem reminded me of an experience of mine; I was once sent to a role-playing game. About 40 Luftwaffe personnel were waiting for the coordinator in a room, and the first the coordinator said upon his arrival was to ask us to remove our rank insignia. Actually, he had expected us to arrive in civilian clothes, but somehow this news didn't make it to us.
Obviously, he knew the answer for my aforementioned question: You're only going to train your mind very well without an authoritarian rank system.
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Could this work in general, outside of role plays? Well, yes. There's an approximation to "no rank system" available; "no substantial difference in rank".
One example: Chiefs of staff could form ad hoc task teams without a leader. All members of the team would have equal or practically equal rank (a captain cannot give orders to a lieutenant without a direct link by the chain of command in at least some personnel systems). They would need to decide on the final conclusion much like a supreme court does; all voices having equal weight*. Influence would depend on exactly the same as in the civilian environment of my intro: Good arguments, reputation and skill in their use.
That, of course, would require that hierarchical authoritarian order is not held too high as an ideal or necessity in the armed service. There would need to be a readiness to accept alternative forms of organisation and even the consciousness about the need for the latter in order to develop the personnel.
*: In case you believe this has no place in the military: It's how certain special forces outfits do their planning in the interest of getting the best out come rather than always the one that the leader had first in mind..