<Reads link> Wait, someone in the Reagan administration suggested building a giant underground complex with nukes so that after the nuclear exchange they could then spend months to dig their way out through a mile of rock, haul the nukes out and set them up so they could say "surprise, we still have nukes?" That's nuts even for the Cold War.
More or less, though it wouldn't be "giant". Think of rail tunnels or something, but deeper. They even built a tunnel bore to test the concept of digging through nuclear rubble that would cover the crater zones precluding deployment of the MX missile launchers, which would be composed of an aggregate of rubble, steel, glass, and atomic ashes:
I think the tunnel bore might have been donated though. This is talked about in Volume 2 of the document IIRC.
The idea of "Deep Basing" is at least as old as Kennedy administration though. The USAF floated similar ideas for Minuteman III, AICBM, and MX, spanning a time period of ~20 years.
More to the point, it's only one method of the so-called "super-hard" basing. Another was to store individual silos at such extreme depths, c.f. Boeing "Sand Silo" and Lawrence Livermore National Laboratory "Pencil Pusher" basing methods which are also discussed in that book.
This isn't even getting into the US Navy's undersea submarine pen-cum-missile silos China Lake was looking at building in the various American Pacific colonies in the '60s (based on deep vein mining technology):
http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0803366
Fine, if the primitives do that, I'll camp a few of my space marines at the point where their tunnel will eventually emerge and wait to shoot them when they come out.
The point is that there are far more imaginative, nefarious, and deceptive nuclear basing methods that could be employed in reality, let alone fiction, to mask the locations, capabilities, and even number of nuclear weapons. The Israeli nuclear arsenal is the obvious example since it's extant, even if their entire nuclear deterrent is some truck trailers in garages and a bunker at an airbase with gravity bombs.
This is a silly argument though. The thread should be discussing how to actually implement this in the game in lieu of not being able check per-tick combats of ground units. The only condition you could actually use is whether or not one side owns a planet. Sort of precludes having your invasion force nuked if the game can't even know what's happening when you're invading a planet. I'm not even sure if you can trigger something to happen if you fail to invade a planet. The Mutant Horror event didn't exactly tell me how my brave space warrior-peasants fought off The Blob with fire extinguishers and liquid nitrogen before the Space Cavalry could arrive with their Space Tanks and Space Cryogenic Container Trucks.