The Katana sword was a signature weapon of the Samurai of feudal Japan. It is a single-edged blade, allowing it to be both thicker and robust at the back of the blade (mune), yet razor sharp at the cutting edge (ha). Its curved body makes it ideal for both the slashing movements common in mounted combat, as well as thrusting moves when fighting on foot. A samurai would typically carry two swords, a katana and a wakizashi (smaller, shorter sword). Together, the katana and wakizashi were known as a daisho set.
The katana was forged using a technique called the Tatara-buki method. This special forging method aimed to achieve three highly desirable qualities in the sword, namely that it could not break or bend and had a razor sharp cutting edge. This was achieved by making tamahagane from iron sand and charcoal in a clay tatara furnace. The resulting steel had a varying carbon content that resulted in a mixture of hard, brittle steel and soft, malleable metal.
Once the blade had been forged, it was polished by a professional sword polisher, known as togishi. This process creates the hamon, the distinctive pattern of differential tempering that is so characteristic of the katana.
A samurai would often further customize their katana by choosing the length of the blade and hilt, and ornamenting it with a variety of designs on the tang (membushi). Other important characteristics included whether the tip was long or short and whether it was curved or straight, all of which were meant to enhance the aesthetic and functionality of the sword. The keywords I will use are