English archers had their longbows, Old West sheriffs had their six-shooters, but samurai warriors had the most fearsome weapon of all: the razor-sharp katana­, or samurai sword, which could slice through a human body with a single slash.

Japanese sword-making was perfected 600 year ago by craftsmen who knew nothing of electron microscopy, mass spectrometry, or other tools of modern science, which are only now revealing exactly why the swords are so lethal. Join NOVA’s investigation of the centuries-old secrets behind the making of this ultimate medieval super weapon. The program follows fifteen traditional Japanese craftsmen who spend nearly six months creating a sword, from smelting the ore to forging the steel and finally to sharpening the blade to its keen and deadly edge.

Running time is approximately 56 minutes.