Well no, the point is he relieves Sinclair and takes command on the basis he our ranks him and has authority from the joint chiefs. Something that shouldn't be possible in a "dis-unified" structure.
I haven't seen these episodes since the original run, so I don't remember particulars. But it would most likely depend on the rules establishing the command. If it was a "joint" operation, which would not be surprising with its diplomatic role, the post would most likely be open to an officer of any branch.
There are different values of "unified" forces. The process by which the US armed forces were combined under the Department of Defense in the late 1940's was called "unification." It did not, obviously, do away with the individual services, but changed they way they were organized and commanded at the upper levels.
As I mentioned earlier, the term "joint chiefs" implies that there are different elements that come together at that level. I know the term was just lifted from the US forces, but it still has an implication. Completely unified armed forces like Canada's don't use words like "joint," it is implicit in the structure.
But, you tell me, if you were in the highly unlikely scenario of the ship's captain being relieved while you were onboard a ship, the fact that you're the next highest ranking officer wouldn't put you in command, or would it?
That he has authority over you isn't surprising in the least, according to our naval traditions, a captain at sea is next in line from god in terms of authority.
Because of the specialized nautical know-how involved, there are normally very strict guidelines as to who is in charge of a warship and who is in line for command. Under US Navy regulations, the only officer that can give orders to a vessel's CO is a flag officer eligible for command at sea. So if the CO is a commander, and there was an O-6 captain aboard, the CO would still be in charge. Likewise if there was a supply corps admiral aboard, or a four-star general.
Still, there is some flexibility if the higher-ups feel it is necessary. A few years ago, a marine brigadier general was given command of a seven-ship expeditionary (amphibious) strike group, flying his red flag on USS
Belleau Wood. That was something of an experiment, and we will see if it is repeated, but the door was opened.
--Justin