“Thus the ground was laid for Dienbienphu, which would equal Waterloo, Gettysburg and Stalingrad as one of the decisive battles of history. It was also Giap’s epiphany. “Years before, I interviewed Cao Xuan Nghia, a Vietminh veteran, whose recollection underscored Giap’s point. He had trekked with his infantry company for forty-five days from their camp…