I've come across a military question which is so subtle that I think it has to be answered from a philosophical perspective, dealing with the meaning of "duty" and nuanced things like that.
In many militaries, the enlisted and officers take different oaths. In the US, the Oath of Enlistment is subtly different than that of the Oath of Commissioned Officers.
From what I can tell, it is generally accepted that these oaths do not end upon retirement. There are many proud veterans who consider themselves to be bound by these oaths still. So that is clear.
What I'm interested in is the effects of an enlisted individual being promoted into the officers corps. In such a case, they will have sworn to two oaths, which are different.
Does the officer's oath supplant the enlisted oath, ending its effects? Is the officer's oath considered to already contain everything in the enlisted oath? There's many philosophical arguments about the fact that the enlisted oath includes an agreement to follow the orders of the president while the officer's oath does not.
These seem like nuanced questions about duty, and I cannot find any regulatory documents on the topic, which suggests to me that this is a question for military philosophy. It strikes me as there should be some historical philosophical opinions on the topic. (And there's no military stack exchange)