Artificial Intelligence

Nuclear submarines used to be used for second strike capability. But now we can replace that with AI, he says. Since these are not vulnerable to attack, you can just wait and see if someone actually notes you too bad for them. And of course, an AI sub that doesn't need room for a crew of 200 or something is much smaller,. Much easier to evade radar to stay for indefinite time underwater and submerge  and all of that.