In ancient Japanese history, countless battles were fought. Though the exact date is unknown, a swords-smith named Amakuni made swords for the Japanese soldiers.
After the battle, the soldiers returned in defeat. Amakuni didn’t understand why such soldiers were beaten- until he saw their broken and useless swords. Seeing that these soldiers needed much heavier duty swords, he worked for days and nights, tirelessly without rest. Days later he returned to the soldiers with his new weapon- the Ninhoto Katana (usually just called Katana) Ninhoto is the name of the sword type in Japanese, and doesn’t have an English name. Katana simply means sword in Japanese, but is usually what people call the Ninhoto katana. But what makes this type of Katana so important?
The Ninhoto Katana is the sharpest type of sword in the world, with a record of being able to chop through 8 prisoners at once (during ancient times, the strength of a Katana was measured in how many prisoners it could chop through at once, gory but true!)This is because of tiny serrations that let it slice through things like butter. It is the only weapon that can slash apart wood, as any other wood chopping things hack at it (using the weight of its head to rush through the object). This attribute has been the inspiration for many blades, like razor blades. Razor blades have tiny serrations, just like the Ninhoto Katana. Also, serrations can be found in syringes (to make them go through skin with less pain). Also, the curved shape of the Ninhoto Katana makes it very powerful, and it will rarely break. The combination gives a powerful and sharp weapon, not to mention that it is light!
You may be wondering how the Ninhoto Katana gets all these amazing attributes. First, is the curve. This is caused because while the Ninhoto Katana is being made, there are two types of metal. This is similar to a composite bow. One side has high carbon Tamahagane (special, high quality alloy made of high amounts of carbon and iron, which is only formed when at the perfect temperature, and cooled properly) and the other side has low carbon Tamahagane. One side expands farther while cooling, and causes a curve. The serrations, unlike other blades, are not caused by monotonous sharpening. It occurs because of the way the metal cools, much like how the curve is formed. Some of the science about Ninhoto Katana is a mystery. Lastly is the lightness. Because the Tamahagane has a lot of carbon, it is very lightweight. This is the logic of how the Ninhoto Katana gets its traits.