In the middle of the Yayoi period(B.C.1), there is no iron-manufacture technology in domestic, the iron material came across the sea from a continent and the Korean Peninsula, and the blacksmith started. It is said that the sword of a visit of those days was superior to the sword of domestic manufacture in steel materials and the technology of manufacture.　Iron manufacture started by the visitor from a continent in the late (1st century〜) Yayoi period. A blacksmith's worker visited systematically his Yamato-Imperial-Court era (the 4-7th century), and new iron-manufacture technology (iron ore iron manufacture) and edge (steel) technology were introduced into them. Iron manufacture of existing iron sand was the different ironing method. Both the ironing method (in San-in, iron sand, and San-yō and a northeast are the tendencies of iron ore by the difference in a technical propagation route) is parallel for a while, and it is considered that it was united at the time of when.
 It is called middle of the Heian period(Around about 990) that the "Tachi" of the curved blade appears through the time of the long "Tsurugi sword" of a domestic straight sword. The "Tachi" shifted to the "sword" in change of the tactics of the Muromachi period through the golden age of the Tachi of the Kamakura period. The new Tatara iron mill of mass production appeared, and "Chigusa Steel "and "Izuha Steel" (Tamahagane of mass production) were produced in the late Muromachi age. Consequently, the Tatara iron mill of every place where efficiency is bad declined rapidly, and this caused the end of a Ko-tō.
 It went into the Keicho age (before Edo opening 1596), swordsmith Horikawa Kunihiro used these new steel materials, and the sword was made by the newly devised method. Iron manufacture and a blacksmith dissociated by development of new mass-production steel and a physical distribution. Bordering on the term of this, change of steel materials brought about the quality of a sword, and the change of how to make a sword. Since the qualities of a sword differ, the sword after it is called a Shin-tō(new sword). The steel materials and the tradition of how to make a sword  of a Ko-tō (old sword) stopped here.
 In the middle of the Edo period, mass production of a Tamahagane was therefore still attained at reform of the Tatara ironing method. It came (Sanyō Rai already uses in the end of a curtain) to call a "Tachi" and a "Katana" a "Japanese sword" collectively after Meiji. Although the old sword before a Keicho age (a Tachi and Katana) holds a very important key on a Japanese sword definition, the historical records of how to make a sword are unknown. Since steel materials changed with a time or methods of ironing an area, how to make a Japanese sword was not universal. The method of ironing a Tatara known at the present is a thing after the middle (modern times) of the Edo period, and the material of ancient times - medieval Tatara iron-manufacture = iron is not yet solved. The iron which the method of ironing a Tatara known at the present is a thing after the middle (modern times) of the Edo period, and was manufactured by Tatara iron manufacture of ancient times - medieval times is not yet solved. "A traditional forging" said in the present age is a how to make a sword after the Shin-tō(new sword) which remains in description, and the present age sword has also inherited this. The steel materials and how to make a sword of a Ko-tō which are the symbol of a Japanese sword are still wrapped in a mystery
 When the steel materials of an old sword are solved, the concept (a Tamahagane and forging) of the present age and the Japanese sword currently circulated widely will be improved. 

The history of a sword was illustrated. The length of a time was expressed with the almost exact relative ratio. One notices the concept of each sword from an old sword to a present age sword asking another meaning through vision. Existence of an old sword is very large. The ancient sword connected with an old sword is also the same. There is no old sword at the reason for having been born suddenly one day. An old sword (Koto) says the sword to which curvature was attached on the extension of evolution of an ancient sword. Although the man "an ancient sword is the category of archaeology" is also, it is a very violent view. The time of an ancient sword ,"Shinogi-zukuri was already completed. Also in order to solve the mystery of an old sword, an ancient sword holds an important key. Although an ancient sword is omitted due to a space here, I want to say, "It is a Japanese sword also without complications 

Ko-tō: The sword before the Keicho age (1596). This sword continued and was made in the long period in 600.
 The structure of a blade ,how to make a sword and  the steel materials of an old sword cannot be solved by modern science, either. An old sword is still a mystery. From iron-manufacture technology of those days, steel materials have presumption with the steel of Oroshi-gane or pig-iron.
 The structure of a blade has much one-piece forging to which each swordsmith elaborated pig-iron. It was very rich in change to the forging which combined soft steel and hard steel, and the laminate constraction.
 Probably, the Tatara iron mill of every place also reflected the local characteristic of a metal in the blade.
 Mr. Kanji Naruse who fixed 2,000 Guntōes in the battle line of North China called it "A Ko-tō goes out well and can be fought, even if it grinds and becomes thin. also the blade of the non-Mei of mass production, the Ko-tō fits fighting most" and evaluated the Ko-tō. The use steel materials of the Ko-tō and the structure of a blade were elaborated from the history of a long battle. 

Shin-tō: The sword after the Keichō age (1596). Since there is a possibility that a blade may break with adoption of a hard steel (Tamahagane), this sword is the blade of the "laminate constraction" which uses soft steel for a core. The world of the peace of the Edo period, since the battle was lost, the essence of a sword diminished and concern gathered for blade beauty chiefly. Many descendant swords which compete only for the beauty of a blade were forged. The sword was reduced to the object and cherished article of investment of wealthy merchants. And in order to raise the asset value of a sword, "the fame sword traditions" filled to affectation was created and amplified.
 It is an Edo term that the sword view was degenerated most.
 The still harder Tamahagane appeared in reform of Tatara iron manufacture in the middle of Edo. It appealed for the last stage of Edo, and revolution to a Ko-tō, and the "Shin-Shin-tō(Furthermore, a new sword, the last stage of the Edo in 1493 and afterwards)" appeared. But, the skin of  the blade of Shin-Shin-tō which uses this Tamahagane became still more monotonous with minerals than a Shin-tō.
　Although the present-day Japanese sword community has put the standard on this new sword for steel materials and a How to make a sword, it cannot be rather convinced to this.

 Import of "southern barbarian iron" (India iron) prospered for the Keichō age and iron extensive demand, and it was used for the sword or the gun. There is a Shin-tō of the Mei of having used "southern barbarian iron" considerably. In a famous swordsmith, "Yasutsugu" of a shogun family's retained first swordsmith is. 90 years continued and import of southern barbarian iron was used for many Shin-tōes. Only by the Tamahagane of mass production, since the skin of a blade changes in monotone, there is a school which mixes southern barbarian iron. There is a sword which attached the Mei of southern barbarian iron also in the Shin-Shin-tō which appealed for the return to a Ko-tō in the second half of Edo. Meiji Era, the Miyamoto Kanenori, and the Hayama Enshin challenged the forging of the Japanese sword which used Occidental iron.
Which is said widely now, is "a Japanese sword is a forging sword of use of only Japanese steel" the absolute conditions of a Japanese sword? If that is right, it will be said that the sword of southern barbarian iron combined use is not a Japanese sword.
Japanese iron did not become steel which can be used if "a forging" is indispensable and does not forge conversely in order to remove many non-iron impurities from the fate of a process. On the other hand, although the purity of Occidental iron is very high, only the difficulty of a forge and the difficulty of a content element have been pointed out rather than the advantage.
Japanese people are the races which excelled in the work which unites foreign culture and is made to sublimate to original culture more from ancient times. Consideration with this viewpoint is not made. The iron maximum demand is farm implements and it is after the late Muromachi period that Tatara iron manufacture of mass production appears. It is not necessary to quote the example of the southern barbarian iron in future generations. It is more natural to also consider ancient times that the sword also used together each of domestic iron and foreign iron from the relation of supply and demand
A sword is a "handicraft" which renders the limitation of the capability which the swordsmith has and is made, and is not the
standardized "product". And how to make a sword from ancient times is "secret work handed down only to  its heir", and there were no universal How to make a sword, universal standard, etc. from the first. There is nothing that can be called the common quality or the common level unified by a name called a Japanese sword.
This is the real image of "an individual handmade Japanese sword" more from ancient times.
If it says without being afraid, can't it be said that a belief and a wish of some people who become modernization and say, "The symbol slack Japanese sword of the Japanese spirit must be domestic iron" were under an illusion soon, and became the myth of present "Japanese sword = Tamahagane and forging" to it involving rights?
Although carried out based on the Shin-tō, the excuse for saving a Japanese sword after defeat of Japan of World War II accelerated this idea further. "The standard and conditions" of a Japanese sword which originally cannot exist begin independence, and seem to have distorted the real image of a Japanese sword.
Although a Ko-tō has presumption with the steel which adjusted pig-iron, there is no proof of having used only domestic steel.
The racial sensitivity, wisdom, and originality and creativity" which raised arms to the region of art are important.
If it is the sword which is equipped with the requirements as arms and charms people, it will be able to be called "Japanese sword" also without complications. There are no steel materials for the purpose of a sword, it is a means to the last and the sword of southern barbarian iron combined use is also the example.
If a Japanese sword is seen on the flowing time-axis, steel materials and a How to make a sword will change clearly.
Pioneering swordsmiths challenged the forging of the Japanese sword which used Occidental iron on the extension.

 Do how, the trend which denies entirely the Japanese sword which stops time, makes the Japanese sword of a certain time absolute basis, and does not suit the condition, considering the history of a Japanese sword? About the arms performance which are the bottom conditions of a Japanese sword, the steel materials (refer to the clause of a practical use Guntō) which were excellent in the after-mentioned exist.

 Probably such steel materials were united and, in addition, there was possibility of the new Japanese sword which had art

 

This site has described everywhere the question of "what it is with a Japanese sword"
The concept of the Japanese sword circulated now is based on the Shin Shin-to of an end of Edo Period. In the history of a long Japanese sword, it is only in one figure of the Japanese sword of the "modern last stage". The Japanese fine-arts sword community said that the steel materials and sword-making method of this sword were a traditional Japanese sword from ancient times, and circulated false information.
The highest Japanese sword is a Tachi(Ko-tō) made at the Kamakura period - the Period of the Northern and Southern Dynasties. A Ko-tō has much one-sheet forging. And the steel materials of a blade are not Tamahaganes. And yet, this blade was superior to the blade of the Tamahagane of a two-piece sword construction.
 The function and beauty of the Japanese sword deteriorated as the Shin-tō - the Shin Shin-tō, and the era fell.
 A Shin Shin-tō is not a Japanese sword from ancient times. "Ancient" thinks that it is the common sense of the history of a sword, and Japanese history which is pointed out from an Ko-tō at least. However, the sword community in Japan defined the sword near modernization as "ancient" accidentally. Steel materials and the sword-making method of the Japanese sword have also been quite broad since a domestic ancient sword.
 In spite of it, very irrational recognition that the blade of the military swords (Guntō) using the new steel materials which were excellent for the narrow-minded concept of the Japanese sword circulated today etc. was not a Japanese sword spread in the world.
The fabrication of irresponsible and intentional the "Japanese sword myth" of a Japanese sword community is spreading in the world. Foundation Japanese Fine-arts Sword Preservation Association is the huge rights organization which picked a fight with the politician. Therefore, nobody has pointed out this error.
This site asks about this error.
The error of the common sense of the Japanese sword is explained to the following items in detail.
Kōa-Issin-tō", "Gunsui-tō", "Shinbu-tō", "Research of the military swords blade", "Talk of the sword in a battle","Guntō evaluation", etc.

 

Contents�U "Forging and intensity", "What is a celebrated sword?", "Southern barbarian iron, and Western iron use", "Inquiring about the common sense of a Japanese sword", "Jigane of a Japanese sword", "House of cards", "Mantetsu-tō's whole aspect", etc.

 

 It is regrettable not to translate these all into English now. All are someday translated into English..