In "Platoon," a middle-class college student volunteers for the war in Vietnam because he considers it his patriotic duty. The first thing he encounters on the airport tarmac in Saigon is a cart of body bags. It's downhill from there: endless hikes, ditch-digging, heat, rain, bugs and snakebites, fear and confusion, sleeplessness, and terror when he finally sleeps. He will only gradually, unknowingly, become an adequate soldier--one who has left...