On this date in 1865, the Japanese samurai Okada Izo was dispatched by crucifixion. He was one of* the “Four Hitokiri“ — manslayers — whose legendary blades coruscated in the Bakumatsu era that marked Japan’s pivot from an isolationist feudal state, one where samurai were big men on prefectures, to a burgeoning modern power ruled by industry and mass conscription. The irony was that dinosaurs like the Hitokiri helped bring the asteroid down on their own heads. During the chaotic Bakumatsu period, triggered by Japan’s becoming involuntarily opened to the outside world, the emperor — long a figurehead marginalized by...