Japan’s famed kitchen knives—celebrated for their precision and craftsmanship—trace their origins to the samurai swords forged centuries ago, a legacy still evident in places like Tokyo’s Kappabashi Kitchen Street. Here, the sound of knife sharpening rings out on the sidewalk. Rows of shiny blades sparkle in shop windows, and purveyors demonstrate how these knives can effortlessly shave a carrot into paper-thin strips. Japan's Unique Weaponry “Japan was actually quite late getting into the Iron Age,” says Paul Martin, a historian and author on Japanese weaponry. Swordsmithing spread to Japan from mainland Asia, he says, and between the third and sixth centuries, Japan started producing its own double-edged swords. During the Heian period (A.D. 794-1185), Japan became more culturally independent with flourishing artistic and literary scenes. The samurai class—elite warriors who served powerful landowners and lords—arose and developed curved swords called tachi used for cavalry.…