The japanese katana sword is the quintessential samurai weapon. They are known for their strength and accuracy (they can split a human body in two) and their artistic beauty as a piece of hand held craftsmanship.
The forging of the blades is a delicate and careful process, as much an art as a technical exercise. Swordsmiths need to have a great deal of physical strength, patience and dexterity. They also must have an eye for the limits of their material and an appreciation of the beauty of a finished sword. They have also developed a style of steel forging called “hamon”, which gives the blade its distinctive look and, to some extent, its practical qualities.
Hamon variations are indicative of the period, smith, school and even place of manufacture of a sword. They may not be immediately apparent to the uninitiated, but they are there, in the tempered martensite between the softer wrought iron core and the hardened steel cutting edge.
Other features of the katana that are unique to it are the pronounced curves in its shape, its kissaki (point) which is not the sharply chisel-like point commonly mistaken for a tanto tip, and its koshirae (mounting). The koshirae includes mekugis (pins) holding the tang, or spike, of the sword in place, and menuki (small ornaments), traditionally used to display family crests.
Production of katanas came to a halt in the wake of World War II, but the sword is making something of a comeback today. Swords are still largely made by traditional methods in Japan, but there is also an increasing number of katana being produced outside of the country.More information here