If you are deluded enough as a national leader that you want to build nuclear submarines, rather than invest in friendship, then today’s invention is for you Generalissimo.
Every inch of the planet surface is now inspected minutely by satellites so that when a new naval vessel is being built, everyone knows about it.
Today’s invention is therefore a factory for building and launching submarines which is itself a submarine.
This would be a semi-automated production line, fitted inside a sub the size of an aircraft carrier (which would have to be built in a land-based dockyard, but disguised as a conventional ship).
This would navigate to random rendez-vous and be supplied with watertight containers of materials and parts dropped over the sides of ships.
In this way, a sequence of new submarines could be launched like torpedoes, wherever was tactically optimal.