Long lists of soldiers killed in wartime can have great emotional power, as anyone who has been to the Vietnam Veterans Memorial in Washington can attest. However dignified and moving, though, in the end such a listing can really describe them only as a group: They wore the uniform and died in the service of their country. But who they were individually, how they served, what they left behind — that is more than a catalogue of names can convey. So here is the story behind just one of the names ''Nightline" will enumerate on Memorial Day: Sergeant Rafael Peralta...