A large submarine with a large crew and a serving of nuclear missiles us indeed hard to conceal, because it needs large coastal facilities.
But IDK if a small submarine with little or no crew, small dive depth, and relatively small payload needs all thus. If a nation-state wanted to deploy it, that could be done way more covertly.
Maybe this is not done because it does not offer any interesting military capabilities. Maybe it is done, but we don't hear about it, because it does offer some interesting capabilities which they don't want to advertise.
> But IDK if a small submarine with little or no crew, small dive depth, and relatively small payload needs all thus. If a nation-state wanted to deploy it, that could be done way more covertly.
In a way, this is tautological. Anything an organized crime group does, a nation state can do trivially, by just paying that crime group (or a similarly-sized and skilled legit group).
The right question is, as you point out, whether it's useful for a nation state to do this. Most of the time it probably isn't - cold war is as much about capability as it is about advertising the capability to the adversaries. If the Russians - or the Chinese, or the Americans - aren't bragging about it, they probably aren't using it in a meaningful fashion.
The North Koreans and Iranians are using very small submarines, similar to the ones under discussion here, probably for similar roles (covert infiltration of people and goods). And similarly, operational security is probably the most important part of their mission as well.
The US fills the same need with the Shallow Water Combat Submersible, delivered close to the target by another submarine in a Dry Deck Shelter. But that's because the US Navy has focused on long range operations.
But IDK if a small submarine with little or no crew, small dive depth, and relatively small payload needs all thus. If a nation-state wanted to deploy it, that could be done way more covertly.
Maybe this is not done because it does not offer any interesting military capabilities. Maybe it is done, but we don't hear about it, because it does offer some interesting capabilities which they don't want to advertise.