5th Column (fan expansion for Fortress America) (2007)

Quoted from the 5th Column Rules Introduction:

With rules easy enough for a novice to understand, yet subtle enough to delight the expert, 5th Column adds the rules and new playing pieces to add increasing realism to Milton Bradley’s Fortress America, while maintaining the game’s ease and speed of play. 5th Column adds the ability to influence your game with unconventional tactics.

Yet the new rules don’t overwhelm the old game. A large army will still defeat a small army. However, in a close battle, long range planning with unconventional forces can tip the balance. New rules and plastic playing pieces are included for fifth column activities, commandeering civilian airlift capacity, radar, and fuel supplies.

Each of the 4 armies has 8 new pieces:

2 × Payoff Units (Dollar Signs)
2 × Fuel Supplies (Oil Rigs)
2 × Radar (Satellite Dishes)
2 × Airlift Units (Aircraft)