The Japanese word ‘katana’ is that used most commonly to identify the deadly curved sword of the samurai: the final evolutionary stage of what is probably the finest edged weapon in world military history. The origins of the katana lay in the straight-bladed swords of ancient Japan, and from these straight swords the tachi evolved, which was the first type of Japanese sword to have a curved blade. Tachi would be slung from the belts of the early samurai – the members of Japan’s knightly class. However, the transformation of the tachi into the katana had less to do with shape and construction than with mode of use. Changes in swordsmanship meant that the sword, sometimes in a shortened form, would be thrust into the belt with its cutting edge uppermost, rather than suspended from the belt. Now the samurai could deliver a deadly swordstroke as part of the action of drawing his weapon, rather than having to execute a two-handed movement of unsheathing and preparation. Such was the weapon that was to become the sword of legend.

   Not surprisingly, the legends and traditions surrounding the katana are inseparable from the culture of the men who wore and used it, because no edged weapon in history has been more closely associated with its owner than the Japanese sword has been with the samurai. To a samurai, one’s katana was both a weapon and a symbol. Never has the relationship between man and sword been better expressed than in the words of the great shogun (military dictator) of Japan, Tokugawa Ieyasu (1542–1616), who advised his successors that ‘the sword is the soul of the warrior’. No samurai would ever be without his sword, whether he was wearing armour or everyday clothes, and a sword forged by a celebrated master was one of the most precious gifts a warrior could receive. The sword, in its rest position thrust into the belt, would tell the world that its owner was a true samurai – a member of a social and military elite – since 4 members of the lower classes did not carry weapons (theoretically, at least). When the katana was drawn from the scabbard – an event that actually occurred mercifully less often than the movies would have us believe – it became the ultimate means of asserting the samurai’s authority.

This modern reworking of an old woodblock print shows a samurai with a katana. Standing with one foot on the plinth of a Buddhist statue, he holds his sword in the raised position. The scabbard thrust into his belt in the classic katana style allows the weapon to be drawn rapidly. He also has a shorter sword, conventionally called a wakizashi.

   The katana was also one of the few edged weapons in history that could be used both as a sword and as a shield: the blade’s resilient and springy inner core meant that the weapon could absorb considerable shock. This factor would not have been present had the entire blade possessed the extreme hardness of the sword’s very sharp cutting edge. In a combat situation the samurai’s first stroke, delivered straight from the scabbard, could be employed either to parry an opponent’s strike or to provide its owner’s own devastating first and final blow – one that would likely save his own life and end that of another.
   The samurai was essentially an individual warrior, and the surviving great swords of Japan similarly have their own individuality: their shapes and polished surfaces with unique temper patterns provide a ‘personality’ as unique as the signatures of their makers on the tang.
   The visual beauty of a sword, the outward expression of an inner power, was fully appreciated by interested European visitors to Japan in the latter half of the nineteenth century. Japan had closed its doors to the Western world for two centuries. Among the pioneers who visited the newly reopened country were enthusiasts for the Japanese martial arts, and swords provided the ultimate level of fascination. One admirer wrote in 1905 that ‘as a weapon of offence and defence a katana is an infinitely superior one to the ridiculous, single-handed sword with its 36-inch blade, with which British infantry officers are armed’.
   By 1905, of course, the katana had become more a symbol of military rank for the Japanese armed forces than an actual offensive weapon. Even in this much reduced role, the long tradition that equated a superlative weapon with a superlative warrior was continued. Paradoxically, however, even though the sword may have played a key symbolic role in the life of the samurai over many centuries, on most occasions when a samurai engaged in actual combat the sword was not the primary weapon of choice. The first samurai made up the private armies of the rich landowners from the ninth century onwards, and they came to cherish and respect most of all the prowess a warrior displayed in kyuba no michi (‘the way of bow and horse’). The ability to deliver arrows from horseback was the military skill that would win most battles, and it was only when the bow, with no arrows left, was passed to an attendant that the samurai would draw his two-handed sword and engage in combat with edged weapons. It is not until the attempted invasions of Japan by the Mongol armies of Khubilai Khan during the thirteenth century that we read of swords being chosen as the primary weapon, and this only when the samurai engaged the Mongols in hand-to-hand fighting on the decks of their ships. Yet for every recorded heroic swordfight with a Mongol warrior, there is an equivalent story of a different samurai felling an invader from a distance using a welldelivered arrow.
   Three centuries later, during Japan’s sixteenth-century Sengoku Period – the ‘Age of Warring States’ – the outcome of battles depended on the deployment of large infantry squads armed with firearms, bows or long spears, and units of mounted samurai who wielded spears from the saddle in preference to bows. Once again the sword was the secondary battlefield weapon. The primary weapon was now the straight-bladed spear, and it is really only in actions undertaken off the battlefield – such as revenge killings or duels – that we encounter the popular image of the individual samurai warrior squarely facing his opponent with sword in hand. Nevertheless, despite the practicalities of the battlefield, the ideal of the samurai as a sword- rather than a spear- or even gun-wielding warrior was to be cherished long after the introduction of modern weapons had made the sword an anachronism. Thus, the battle of Kariwano – the final conflict of the Boshin War of 1868 – finished with a suicidal charge using swords, and during the Satsuma Rebellion of 1877 the followers of Saigo Takamori climbed the walls of Kumamoto Castle, katana in hand, to receive the bullets of the imperial army.

This hanging scroll from Shimada Art Museum, Kumamoto, shows Miyamoto Musashi, the most famous and enigmatic of the kengo, in characteristic pose armed with a sword in each hand. Musashi was renowned for his ability to wield a katana and a wakizashi at the same time.

Katana: the soul of the samurai

Even for the uninitiated, the first encounter with a fine katana cannot fail to provoke the kind of impressions that the Japanese sword has inspired throughout history. A single glance will suffice to convince the newcomer that here is an object that, with its icy sheen and inner strength, is both a weapon and a work of art. Add to this two further realizations – that the artistry that created its complex surface appearance directly reflects the quest for perfection in a weapon, and that the techniques that first brought all this about are today lost to history and merely presumed – and one’s appreciation of the object’s uniqueness is complete.

   The metallurgy underlying a Japanese sword is exceedingly complex and finds visual expression in the surface anatomy of the final blade. Every detail of the finish has some bearing on the sword’s quality, and the development of these microtechniques has left a trail that can be traced back many centuries. Because of these qualities and the historical dimension they represent, this section of the book will start with the forging of a blade, thereby introducing the technical language that is required before one can fully appreciate the historical development of the sword from the straightbladed weapon of antiquity to the curved blade of the katana.

Even though none of the actual techniques used by the early swordsmiths was apparently ever written down, the smiths’ traditions are so strong that even today some superb swords are made using the presumed methodology of a past age. The creation of a fine katana was, and still is, a matter of tradition and religious solemnity. The presence within the swordmaker’s forge of a kamidana, the Shinto ‘god-shelf’ found in many Japanese homes, proclaims that this is a sacred space; this is also acknowledged by the humility of the craftsman himself. As often as not he will refer to himself simply as a kajiya (blacksmith) rather than a tosho (swordsmith). The kami (deities) will first be invoked before the swordsmith, clad in white robes resembling those of a Shinto priest, begins the long and arduous process of transforming raw materials into one of the country’s finest finished products.

The premises of a sword polisher, whose craftsmen are putting the final touches to a fine blade using traditional techniques. The figure on the left is polishing a finished blade with a cloth, while the figure on the right is sharpening a blade using a whetstone and abrasive slurry. This is a print from the Meiji Period, based on a medieval painting.

   Nowadays, steel for swords can be obtained from sources outside Japan. However, the early swordsmiths were also iron producers: the raw material for a Japanese sword came from the surrounding environment. Beside some rivers in the coastal areas, particularly along the edge of the Inland Sea, were to be found deposits of satetsu (iron sand). The term itself indicates the composition of the sand. This rare ore would be smelted in small primitive furnaces at 1300–1500ºC to produce tama hagane (raw steel pieces). The best pieces, with a carbon content of 0.3–1.5 per cent, were then beaten into thin cakes, and the expert tosho would select the ones most suitable for swordmaking.

In this beautifully observed model in Aya Castle, Miyazaki Prefecture, we see a swordsmith kneeling while his assistant wields a large hammer. They are both dressed in ceremonial white robes and wear lacquered eboshi caps. The sacred atmosphere is confirmed by the kamidana (god shelf) on the wall behind them and the hanging shimenawa (sacred rope) that indicates that the space within the forge is holy ground.

Chemically speaking, steel is a combination of iron and carbon. Pure iron is too soft to be given a sharp edge. The more carbon is present, the harder the steel will be; however, too much carbon will make the sword brittle. The skill of the early Japanese swordsmiths lay in their ability to control the carbon content despite having no knowledge of modern metallurgical processes or access to microscopic viewing techniques. Quite how they achieved this will remain a mystery. However, the results of their work, in the form of the peerless weapons they made, provide amazing evidence of how successful they were. Another difference from modern steel-production methods is that the steel of a Japanese sword was never heated sufficiently highly to melt it, so in the finished product a degree of heterogeneity survived. Yet it was this very lack of uniformity that was to yield the classic weapons.
   We now know that when steel with a carbon content of 0.7 per cent (the usual proportion found in Japanese swords) is heated to 750ºC it becomes a substance known as austenite. This has an open crystalline structure and in it carbon atoms combine readily with iron. When austenite is cooled rapidly its crystalline structure changes so that it becomes martensite – a compound that allows the locking of carbon molecules into the iron to produce the hardest form of steel. However, if austenite is allowed to cool slowly it produces, among other substances, a softer steel called pearlite. It was by producing these two forms of steel and then combining them to make a blade that the Japanese tosho were able to create a weapon with a super-hard cutting edge but also a resilient body that would absorb the shock of impact. The change in surface appearance along the length of a Japanese blade, a feature readily noticed when one examines a good specimen, marks the transitional zone between the martensite crystals of the hardened cutting edge and the softer pearlite of the body.

Tama hagane (raw steel pieces) resembling small flakes and produced from the smelting of satetsu (iron sand) are piled up ready to be put into the furnace so they will fuse together. (Osafune Sword Village)

This demonstration piece shows how the repeated folding of the steel billet was achieved. The existing billet is notched using an axe above a frame and then beaten back on itself. (Osafune Sword Village)

One of the most dramatic demonstrations of the strength and resilience of the katana blade, a quality most cherished by the swordsmiths, was provided in 1860 when Ii Naosuke was assassinated by loyalist ronin as a punishment for his co-operation with Western powers. The attack took place just outside Edo Castle.

The basic structure of a Japanese sword is therefore a duplex one, with different types of steel, although multiple combinations are also to be found. The simplest twofold design has a soft inner core, the shingane, which has a lower carbon content than the outer skin, or hadagane. This outer surface is of harder steel that will provide a cutting edge; the softer inner core will give resilience.

Several of the finer points of a finished blade are illustrated by this fine example of a katana on display in the Kaisendo, Kaminoyama City, Yamagata Prefecture. There is a very pronounced temper pattern (hamon) that marks the interface between the harder steel of the cutting edge and the softer and more resilient steel of the body. The shinogi (ridge) runs along the blade to the kissaki (point).

   The sections were created and initially treated similarly. First, the pieces of tama hagane, which look like rice crackers, were carefully piled up on a long spoon-like object with paper tied round them to hold them together until they were placed in the furnace. At a temperature of about 1300ºC the pieces began to fuse together. The result of this was a basic block of steel. This was broken up and, after checking that any visible impurities had been removed, it was re-forged. The steel billet resulting from this was repeatedly heated and beaten. The billet was continuously folded back upon itself so as to create a complex structure with several layers. The folding was achieved by notching the red-hot billet using an axe-like implement and then hammering the billet against the angle.
   The difference between the hadagane and the shingane in terms of processing lay simply in the number of foldings. The outer hadagane received the most foldings, which determined its relatively higher carbon content and its ultimate level of hardness.