He goes around the base to give things an inspection, hoping he can make a few changes to improve things. Only half way through his inspection, he finds a private stood next to a bench, seemingly doing nothing.
Commander: Private, what are you standing around for?
Private: Sir! My orders are to stand here and make sure nobody sits on this bench, sir!
Commander: ...Why?
Private: I'm not sure, sir! I was just told to do this by the previous commander!
Utterly confused, but unwilling to let the mystery lie, the commander makes a call to the previous commander, now promoted to brigadier.
Commander: Brigadier, sir. I just gained control of Fort Naimheer, and I was wondering why you ordered a man to stand next to a bench and tell people not to sit on it.
Brigadier: Oh, that guy? Yeah, I didn't give the order to begin with. I just figured the other guy had a reason for it, so I left it alone.
Now even more confused, the commander makes contact with the general who led the base before him.
Commander: General, sir. I just gained control of Fort Naimheer, and I was wondering why you ordered a man to stand next to a bench and tell people not to sit on it.
General: Huh? Oh, that? It was a standing order. Before my time, you see.
Commander: Figured as much. Do you know who first issued the order?
General: Oh, I believe so. He's retired by now, but I could get you in contact with him.
Finally, the commander makes contact with the veteran, a former commander like himself, who first made the order.
Commander: Hello, sir. Sorry to interrupt your retirement, but I just gained control of Fort Naimheer. Is there a reason why there's a man standing next to a bench and telling people not to sit on it?
Veteran: ...Is the paint still wet?
I've always viewed that joke as a biting criticism of tradition.
Oh, it absolutely is. Tradition for tradition sake leads to so many bad practices.
There's a not entirely implausible chain of events from this private guarding the bench to a post-apocalypse cult centered around that same very bench.