On caching, I just read on another board about "Operation Gladio" and related plans.

These were plans made by NATO forces for 'stay-behind' groups of soldiers following a Warsaw pact invasion of their countries. The soldiers would organize and lead groups of citizens in attacking the enemy.

It seems that some (most) of these groups were to be supplied from caches that were built and stocked...in some countries, they were then forgot, and discovered during construction years later (how cool would it be to be digging a foundation for your garage and discover a cache with weapons, ammo and supplies for 50 people?)

A similar concept is in Vanderboegh's book "Absolved" where a misdirected from WWII railcar laoded with supplies plays a role.

The concept is probably valid: Problems include collecting the materials in the first place (obviously), packing them securely (the military is REALLY good at that sort of packing), emplacing the cache, and of course, security.