In many survivalist stories the intrepid heroes wisely (given the impending plot line) decide to build and stock a fallout shelter. When the inevitable catastrophe comes they move into their underground bunker and live in relative comfort while the bulk of humanity perishes in the event and aftermath. An underground bunker makes good sense for threats like bombs or other large general threats, but it seems like that is all an underground bunker can reasonably defend against.
Underground bunkers that even a wealthy survivalist could build appear to rely on a strong door and concealment for survival against assault. That being said the strong door isn't a true deterrent since the air vent/intake must be exposed. If that air intake is blocked or restricted with mud or a plastic bag and some duct tape the only option for the inhabitants is to sally forth. Given the extremely limited egress points from the shelter these are easily covered by a small assaulting force.
So how can an underground bunker be reasonably defended against roving bands of bandits? Especially considering the cost of blocking an air vent/intake is exceedingly low compared to the cost of defending the air vent/intake. This is the opposite of a defensible position. What tweaks would be needed to make an underground bunker defensible?
Key assumptions:
- Current Tech
- No access to extreme amounts of power like a nuclear power plant in the bunker.
- Completed bunker must be affordable enough and reasonably attainable for a wealthy survivalist or a small group of wealthy survivalists
- Location is rural continental United States