The Trenches of World War I
The Prisoner's Dilemma in the Classroom

You are a soldier in a war that was supposed to last a month, two years ago. You are trapped in a trench, and because of modern armaments, you can be cut down and killed any time you venture out. Similarly, with your weapons, you can easily shoot to kill any enemy soldier who ventures out of his trench. When you are in your trench, you are much safer than outside, but you may often have to go outside to collect the dead, assist the wounded, or just relieve yourself in a place that won't leave you slogging through your own (and your comrades') urine and bowels for weeks and months on end. With this in mind, your decision (and the enemy's) is to shoot to kill, or to refrain from shooting.

• If you shoot to kill at every opportunity, and the enemy does as well, you will be trapped in the trench without opportunity to leave it for any reason.
  
  
• If you refrain from shooting, and the enemy does as well, you will be safer from sniper fire and will be able to leave the trench. However, the war will last longer due to inaction.
  
  
• If you shoot, and the enemy doesn't, you will have moved closer to winning the war; the enemy soldier you shoot dies.
  
  
• If the enemy shoots, and you don't, the enemy will have moved closer to winning the war; you will die.
  
  
• Note that "Move to Win" > "Safer, Longer War" > "Trapped" > "Dead,"
  and "Safer, Longer War" > average of "Move to Win" and "Dead"