The Broken Battlefield
Once upon a time, there was an ancient battlefield, on which many a war had been won or lost. The generals knew it well. But then one day the earth shook. The quake broke open a wide fissure all the way down the middle of the battlefield.
From then on, whenever the generals sent their armies there, their men and horses would fall into the fissure, and battle was impossible. The generals would then withdraw; but they always returned, to find the fissure still there.
Insanity is doing the same thing over and over while expecting different results.
Jonathan Schell compared the condition of war in the nuclear age to this.