A small monument next to Truc Bach Lake celebrates the downing of McCain’s plane. “The citizens and military caught Pilot John Sidney McCain,” the statue’s engraving says. “This was one of 10 aircraft shot down that same day.” But in the days after McCain’s death, this monument has been transformed into a makeshift shrine. Admirers have been laying flowers, incense and money at the statue. The US Embassy in Hanoi laid a wreath there. … Nowadays, Hoa Lo Prison is a state museum, frequented by throngs of young tourists dressed in shorts and sandals. … From 1968 to 1973, Duyet...