I suppose the great historical invasion might work: foreigners land on our shores and set up their strange and terrible machines. The bring diseases that ravage our population, leaving us weak in the face of their incursions. Despite a few desperate battles on our part, the slowly force us back onto "reservations" and try to stamp out the last vestiges of our culture by shipping our young off to concentration camps, err - schools, where horrific punishments await those who try to remember who they were... At least the terrain part will be easy!