He bowls overhand.
I think that this is at the heart of the issue that the USN is facing. It would not be fast or cheap to replenish nuclear subs and carriers, so we generally don't want to use them in scenarios where risk to losing these assets is moderate or high. That's where we get into the cause of the 'zero-defect' mentality that no loss of Ao is acceptable.Well everyone and everything in the military is expendable to some degree. A person or asset that can’t be risked can’t really be used.
There are fewer sub CO eligible people, but there are proportionally fewer sub CO billets; a loss of a single sub CO doesn't really move the needle since there are plenty of CO sub support screened O-5s who can be called up to a CO at sea billet, and plenty of post-CO squadron deputies who can fill in temporarily (and in fact several are relieved each year for various reasons).My take would be that there are many more people that are ready to step in and be a BN Commander that a submarine captain. As a person, they are equally as important, but militarily the sub guy's loss would hurt more.
Thus I don't think that either one particularly 'hurts more' in that there is depth on the bench in either case. With the amount of time it takes to construct a new SSN (years), there is plenty of time to train up new COs through the normal pipeline in the event one or more was lost at sea.
I don't think that this culture is engrained in the Navy as much as it is in the Army and Marine Corps. As a service, we tend to have very strict dividing lines in our culture (chief vs. blue shirt, wardroom vs. enlisted, front office vs rest of wardroom) and we don't, IMO, train people to really cross them until they get picked up for the job or are sitting in it.It's a good comparison and they're close to equivalent scenarios. The surviving personnel in either case should still be able to function with 90%+ unit effectiveness and for the same reasons, that everybody in the unit is trained to understand something about their immediate boss' job, the importance of commander's intent, how the unit's mission fits into the big picture. All that stuff is common across all of the services.
As for the sub scenario specifically: I don't think that a typical DH could effectively fill in for the XO's role in combat because they haven't been through the same training pipeline nor done the reps with the crew. To be clear, when I say that, I mean if the XO were to become incapacitated on short notice and there isn't dedicated time to fully train up the DH to act as the XO's battlestations role. For that matter, if an officer did their DH tour on a SSBN, it is going to be difficult for a seamless transition for the XO to fill in for the CO because SSBN DHs get almost no experience conning the ship and making in-situ decisions on mission - which is the role served by the CO in combat (this loss of experience is usually very noticeable, even for some COs. An SSBN DH's job is almost exclusively administrative). Developing this skillset among DHs on SSNs takes a lot of dedicated bandwidth on the ship and mentorship from the CO, and it's hit-or-miss whether that happens. When it comes to DHs acting in the XO's role during battlestations - it's significantly more miss than hit. DHs will usually act in the COs role when training the bench because that's what is required for command qualifications.
We also haven't dealt with large-scale losses in some time, so it's not really a priority.