I'm reading Tom Clancy's
The Hunt for Red October again. For those not familiar with the plot (c'mon: it was a major motion picture, too), Soviet submarine Captain Ramius and his officers attempt to defect to the United States, bringing their extra special ballistic missile sub with them. Early in the story our hero, Jack Ryan, gets wind of the plot and embarks on a mission to aid Ramius in making it safely across the Atlantic. Of course the Russians will have none of this and do everything in their power to stop Ramius.
A key plot device throughout the book is that Ryan is operating under the assumption that the best he can hope for is to get Captain Ramius and his officers alive, but that they will have to give the submarine back. If he's lucky, the US might get to do a "saftey inspection" first. After all, you can't hold the 100 person crew against their will; they didn't know what was going on and are mostly just conscripts. And once you let them go home the Soviets will know about the sub and want it back. At this point it's more expedient politically to return it than not. Much of the suspense of the story hinges on what an intelligence coup it would be to get the sub without the Soviet Union knowing.
I'm reminded of a line from the movie "Dr Strangelove":
Of course, the whole point of a Doomsday Machine is lost, if you *keep* it a *secret*! Nuclear submarines are no different. They are the kind of weapon you hope never to use: a deterrent, not a real option. As a deterrent, the more you know of the weapon's capabilities, the more you fear it and the more effective it becomes.
With that in mind, it seems to me that given this scenario the best course for the Soviet Union is to negotiate with the American side to allow Captian Ramius to defect, but take instant possession of the missile sub the moment it docks. In this way, they would ensure the Americans get to see
just enough of the boat to be aware of the threat, without learning any new secrets of the implementation. They would lose Captain Ramius but they've lost him anyway, and by negotiating with the Americans up front they could create terms by which they are unable to debrief him.
But then there'd be no book ;)