The Samurai sword would be more properly defined as any Japanese sword wielded by Samurai or Bushi, as they were known in Japanese history; however modern films and television shows have incorrectly portrayed them to be only the well known katana, and very rarely use the proper terminology or classifications of true samurai swords.
To uncover the history of the samurai sword we have to revisit the past during the period of the Middle Ages when the use of steel instead of bronze for bladed weapons vastly improved, single edged swords became more popular throughout Asia, and the production of the Japanese Tachi and Uchigatana began. Japanese Swords, or Nihonto are the traditional bladed weapons used during all of Japanese history. The Tachi was mainly used by cavalry with the cutting edge faced down and the curvature closer to the sword hilt. The Uchigatana was mainly used by foot soldiers and worn edge up from the belt with the curvature closer the sword point. With the evolution of military and feudal society during these times, an entirely new class of warrior emerged. They were the masters of the art of war and evolved from being simply employed as protective guards serving powerful leaders, into a completely dominant class of there own, the Samurai.
This led to the establishment of a feudalistic military that then established the Ways of the Bushido, dominating the Japanese social structure for the next 700 years. Their primary role as military knights included total and absolute allegiance for whom they were pledged to fight and if need be, die defending, which resulted in the need for a superior single bladed weapon to use in close quarter combat as well as defence. Their demand for these high quality weapons produced next generation swords of unrivalled perfection, as they had to be flexible enough to withstand direct impact without breaking, but also had to be hard enough to retain their sharpened edge.
Only the most experienced Japanese sword smiths were able to develop the forging and heat-treating methods that resulted in swords that had both of these properties, which were eventually named the katana. Even the katana itself varied greatly in style during the course of the history of the samurai sword. In the late 14th and early 15th centuries they tended to be two and a half feet long, but by the early 16th century the length was adjusted to two feet with a circular or squared tsuba hand guard and a wrapped grip that could accommodate two hands. These Katana Swords were often accompanied by the similarly made but smaller swords Wakizashi or Shoto, and the two weapons together represented the social power and personal honour of the wielding Samurai.
After many periods of war throughout Japanese history the art of sword making deteriorated and it was not until the Shinshinto Era that sword smiths returned to the forging of superior quality blades after rediscovering several lost techniques. As quickly as the Era began however the Meiji Restoration was passed which banned the possession of all Samurai Swords as arms except to a certain privileged class. As a result the ancient master sword smiths began to conceal their forged blades in simple walking sticks so that the soul of the samurai would live on, and the art of superior sword making would survive and not be lost.