Legend has it that the katana was invented in the 700BC period in Japan along with the folded steel process. History however, feels differently and facts show us that it is possible the folded steel process was brought in from China during trade.
Swords forged between 987 and 1597 are called koto (lit., "old swords"); these are considered the pinnacle of Japanese swordcraft. Initial swords that were made tended to have the curve at the hilt (handle) while swords made later had the curve move up the blade and closer towards the center of the blade.
Swords were usually worn with the cutting edge facing down and mostly on the left side. Why would someone wear the cutting edge up you might wonder. That is true, one would need to be either masochistic or stupid to attempt to pull out a sword edge first! The previous statement however refers to other methods of wearing swords like those hung on the back (both vertically and horizontally). That it was worn on the left is probably attributable to the fact that a large number of the warrior class people were primarily right handed so that their
Iaijutsu (sword drawing technique also called Iaido) was more powerful when drawn with the right hand than with the left. Sword fighting however, required the use of both hands to hold the sword. A sword worn in such a manner (left and edge down) is called
"Tachi". Wikipedia also cited that the signature on the sword (Called
Nakago) would be inscribed in such a manner that it would always show on the outside when worn.
Inital japanese swords were not curved like the modern day Katana. They were in fact straight like the original longswords.
However, during the Heian period curved swordmaking techniques were developed to serve the use of the military. Military at that time consisted mostly of Cavalry and using a straight sword from horseback was
far less effcient when compared to fighting with a curved sword. A curved sword added to a better downward thrust.
