The rich, black loam of Italy's Po River Valley is fertile soil for the seeds of discontent. There, in a densely overpopulated farmland whose every square mile must support 470 people, 80,000 field hands seek work on a puny 132,000 acres of farmland, get their wages—if any—in the wheat and sugar-beet yield of the land itself. With holdings averaging 20 acres or less apiece, the farmers are themselves poor, bitter, hard pressed. For years the richest harvest reaped in the Valley has been one of violence, distrust and hatred.
Last April, seeking a...