Invasion Caches
Based on what records exist, there were one thousand of these built in the USA in 1954 and 1955: twenty to a state, including what is now Alaska and Hawaii (ironically, the most well-preserved Invasion Cache publicly found to date was located outside Anchorage, Alaska). However, no Invasion Caches have been found in Puerto Rico, or any of the USA’s other overseas territories. Presumably, the government agency who built these decided to make the reasonable assumption that Alaska and Hawaii would be states before too much longer.
Every Invasion Cache is built into the land, with an internal power source and a ventilation system that can be sealed from the inside. Each one stocked two years’ worth of food and potable water for six adults; hand-powered batteries; an extensive library of books on survival, medicine, propaganda, and insurgency tactics; work stations for electrical engineering, demolitions, and reloading ammunition; enough bolt-action rifles, supplies, and ammunition for a battalion of irregular infantry for up to a month; roughly ten pounds of unmarked gold discs and other durable trade goods (the wines in particular aged well); and instructions on how to rig the whole complex to explode, if need be. An Invasion Cache is designed to allow up to twenty people to live there more or less indefinitely, although they only come with enough actual beds for six. Entrance to the Cache is secured by solid doors with enough solid locks on them to dissuade casual trespassers, or even curious urban explorers. There’s also always an escape hatch somewhere.
What’s left unmentioned is what exactly Invasion Caches were for. They’re not military, aren’t designed specifically to be fallout shelters (although they effectively are anyway, at least in the short term), have virtually no integral communications capacity (and as little electrical wiring as possible), and their contents are designed to last as long as possible (dried food in newly-found Invasion Caches is probably off at this point, but the stored water containers were designed to last for centuries). They also weren’t built by either the US military or the Federal Civil Defense Administration: what few documents exist on the subject reference a “Strategic Resource Planning Commission,” which nobody’s ever heard of.
Tracking down the original builders of a found Invasion Cache is possible — the SRPC apparently liked to hire local — but not likely to be informative. The land was purchased by the federal government for a reasonable price; eminent domain was never used, or even threatened. Building and supplying the Caches were handled via standard, even boring government contracts that were paid in full, and on time. When asked by curious locals, federal agents overseeing the construction invariably called them ‘Civil Defense projects’ and implied that they were military bunkers, which is not really correct. What Invasion Caches effectively are instead are premade shelters for guerrilla groups, the US government built a thousand of them, and then the US government promptly forgot about them — to the point where nobody in the government can remember why they were built in the first place.
Which admittedly makes them a dandy place to hole up, once somebody finds one. And that, indeed, might be the point. After all: if the government doesn’t know where they all are now, then Invasion Caches should be even more obscure after the (hypothetical, surely) Invaders appear…