How many bomb shelters can be built to protect huge masses of people in every city? Start building now. With a warmonger Bolton and a button-pushing prez who likes to test his toys I think it is going to be inevitable. There are no cooler heads to prevail. The doofygoofylucy prez does what he wants when he wants to whom he wants however often he wants and no can stop him. They are all chickeny scairdy cats. Those who have no stomach for it are bailing..quitting..leaving. The jobs will be wide open for DEMS. We need Bomb shelters to hold 100,000 people in each location with enough sanitation facilities so we don't die of disease, food, water, medical supplies, beds, blankets and air purifying systems. Anyone good with numbers who can tackle the cost? How far will $25 billion go?
Nope.
It's so simple to build a "burrowing" weapon.
Stationary defenses are always rendered obsolete by newer weapons.
That's why we don't build castles as military posts anymore. (And why France doesn't defend the Maginot Line.)
So even if you could build something "impenetrable" against modern weapon technology ... that just creates a challenge for future weapon designers. And it would only be a matter of time until someone figured out how to use technology - perhaps a "rail gun" or energy weapon - to defeat the defenses. And for far less money than it cost to build and maintain the fortress.
Even Cheyenne Mountain (NORAD) is on the verge of becoming obsolete as a shelter, due to advances in technology.
And let's be honest ... in case of large scale nuclear/bio/chem warfare ... or to shelter from an Extinction Level Event (EG: asteroid hit) ... you would have to stay in the shelter for generations before the surface was habitable.