The following extracts are from Tameshigiri no Shinzui (the Essence of Test cutting 1980). This was translated by Gavin Poffley and published as The Spirit of the Sword in 2013. Those of us involved in that project chose this text because by and large it accurately and most fully represented his views on swords and swordsmanship. The material below was reproduced with very little change in his later books including his last publication Nihonto Seishin to Battodo (published 2001).
‘Study into pre-existing blades.
Of the sharp swords used for iaido practice, not all but a large majority will have been forged and bought as a pre-existing stock item and not tailored to the user. I would thus now like to look in to the specifications swords in general, and these pre-produced blades in particular, for the reference of all practitioners of the sword arts.
Japanese swords are categorised into four historical periods depending on when they were forged. These are koto (lit: old swords, forged before 1596), shinto (lit: new swords forged between 1596 and 1760), shin shinto (lit: new new swords, forged between1761 and 1876) and gendaito (lit: modern era swords, forged from 1887 onwards).
Among modern day iaido practitioners there are not many who own a sword that is well balanced for them personally and I would estimate that around seventy percent are not using suitable blades.
I would thus like to consider this point in general, looking to my own experiences with tameshigiri.
There are very few swords in existence that fit well with their user and are balanced in just the way they require to move naturally and harmoniously. Most are forged by swordsmiths using their own unique methods and to their own stock specifications and modern day iaido practitioners will try to adapt their technique to the idiosyncrasies of the blade in their training.
Using a badly balanced sword is a prime cause of the holes in technique that can be seen in many aspects of a swordsman’s performance at demonstrations. One wonders how many of those training in iai bear in mind the following points when selecting a sword:
1. Blade length
2. Weight
3. Curvature
4. Overall appearance of the sword
5. Blade width
6. Nature of the hamon
7. Cutting ability
8. Flexibility of the blade
9. Positioning of the menuki ornaments
10. Positioning of the holes for the pegs that secure the hilt to the blade (mekugi ana and hikae mekugi ana)
11. The length of the tang
12. The practicality of the fittings.
These points summarise the important specifications to pay attention to when selecting a sword for use in iaido training (Img. 1)
To preserve valuable historical swords, when selecting a sword for use in tameshigiri I will purposefully avoid blades of renown with engravings and instead will purchase a nameless blade with a few scratches on it
Swords like this will often have various problems, such as being too long, too heavy, not having much of a curvature or having a tang that is too short. In order to make these suitable for use it is important to carry out the following kinds of modifications to improve the balance:
1. For longer blades, move the hilt fitting grooves (machi) up the blade and resize it to more convenient dimensions.
2. For blades lacking in curvature, have them altered to curve more.
3. For blades with a short tang, have the base of the tang extended.
4. For blades that are too heavy, have a groove put in to lighten them.
Swordsmiths do not often have technical experience in the actual methods involved in using the swords they make and so will largely not understand the correct balance that is required. There are some smiths who create blades bearing in mind that the true essence of the sword is in being able to cut, but most smiths today look at the forging mainly in terms of creating artistic pieces. There are an especially large number of smiths who try to imitate the great works of the koto and shinto periods and the swords they produce are judged by an appraisal panel from a museum, being passed or failed for a certain grade. That such smiths look to artistic merit as the primary concern when making new swords is an entirely understandable and unavoidable situation but still unfortunate.
In the koto period, swords were sometimes forged by smiths who were illiterate and these stalwarts would live for the making of the sword to the exclusion of all else- battling with fire and iron, with the creation of a cutting edge being all-important and the letters that would go on the tang being of little concern. As we can see today, these blades have come to be marked out and revered as swords of great importance or even national treasures. Compared to this what can we say about modern sword forging? Because swords are made primarily as art these days it is often that we see the smith putting more attention into making the tang beautiful than the blade itself, trying to make the inscription as attractive and aesthetically pleasing as possible. There are even cases of modern swords being elevated to the status of blades of renown (meito) solely on the virtues of a pretty tang, designated as prefectural cultural treasures and the smiths that forged such pieces being awarded the honoured status of human national treasures.
1. Length
The standard length for sword blades as specified by the Tokugawa bakufu was two shaku and three sun (approximately 70 centimetres), with variations of between two shaku and two shaku and five sun depending on the height of the user.
The standard length of the military swords (gunto) issued by the old Imperial Army and Navy was two shaku and two sun (approximately 67 centimetres).
Img. 2 Checking for correct length of blade
The swords used in modern iaido practice are generally between two shaku and three sun and two shaku and five sun (between 70 centimetres and 75 centimetres) with swords longer than this only being used by special individuals. If attempting tameshigiri using a sword longer than this, and the blade turns out to be slightly weak, it can snap clean off from the rebound of the strike, especially if the cut is made at an incorrect angle or trajectory.
When I had the honour of meeting the great master of iaido Nakayama Hakudo sensei, I enquired as to the appropriate length for a sword. He told me that a length of one’s own height minus three shaku (around 90 centimetres) is a good length. In my case I am five shaku and four sun (approximately 164 centimetres) in height, and so this would mean that a blade of two shaku and four sun (approximately 73 centimetres) is optimal. However, this length is only optimal for solo iaido kata cutting the air and is slightly too long for tameshigiri. This fact is illustrated by a sword I was gifted with after the War by the archaeologist Ikeda Kenji sensei, who hails from Namamugi in Yokohama’s Tsurumi ward. The blade was two shaku and five sun (around 74 centimetres) in length and forged by Kagaju Sadatoshi in the Bunmei era, making it a koto period sword. I used this sword for tameshigiri for around five years, but it would always bend when my grip control was even slightly at fault.
As the wielder stands up straight the sword should be long enough that the tip just brushes the ground (Img. 2)
As a result I now use a blade of around two shaku and three sun (approximately 71 centimetres) for my own tameshigiri practice, and recommend to my students and the members of my organisation that they use a sword of between two shaku and two sun (approximately 67 centimetres) and two shaku and three sun (approximately 71 centimetres).
6. Depth of the hamon
Between a third and a quarter of the blade’s overall width is a suitable depth for the hamon on a sword for practical use. In general blades with flowery and deeply applied hamon have a tendency to be brittle and thus chip or snap easily.
7. Position of the menuki ornaments on the hilt
During the Muromachi period most sword fittings were in the handachi (cavalry half-sword) style, where the menuki ornaments were wrapped on the right-hand side of the hilt when the sword was at rest with the blade facing down. The military swords of the old Imperial armed forces also had their hilts wrapped based on this style but in this case it meant that the ornaments would fit into the user’s palm, making the grip more fluid and bringing out the user’s technique.
The fittings of the Edo period, by contrast, were the opposite of this and had the menuki on the left-hand side.
Having the menuki too high up the hilt is also not good for handling. They were originally only ornaments to decorate the hilt and thus not necessary. Having said that, menuki can aid one’s technique if wound into the hilt in the handachi koshirae style.
Ninety percent of the swords used by modern day iaido enthusiasts have fittings in the style prevalent in the Edo period.
8. Presence or absence of a groove (hi) in the blade
A sword with a groove running down the blade will make a sound when swung and so many are not fond of them, especially among high-ranking practitioners. On the other hand there are those who like blades that make a sound.
In period films and plays the swooshing sound effects from a blade groove increase the dramatic effect and are generally appreciated by the audience. Additionally, to beginners, the sounds from a blade groove give them the impression that their technique is good. The same is also true of iaido demonstrations where, although it may not impress experts, the audience in general see a performance where sounds are made as being more impressive.
There are tales which suggest that it is impractical to use a sword that has a groove in some situations because it would make a noise even in the dark of night. It is also said that, in the past, the groove was known as the “blood runner”, and acted as a channel so that the blood from a cut or thrust would flow away. Another tale would have it that, when thrust through an opponent’s body, the blade would sometimes get stuck from the pressure so a blood groove was there to ease that pressure and aid blade withdrawal.
Additionally, even though it has no effect on a sword’s cutting ability, the presence or absence of a groove will influence the sword’s weight and is thus also related to balance.
On top of this, when looked at from the point of view of the physical dynamics of a blade, one with a groove will be slightly weaker than one without. However, it will also have a greater flexibility. This can be clearly understood when one notes that exactly the same structure and principle is seen in the construction of a railway track.
Finally, the overall appearance of a sword with a groove is more elegant and appealing, and there are many who prefer this.
9. Effects on cutting ability from the height of the blade’s ridge-line (shinogi)
The cutting power of a Japanese sword will vary based on the individual methods and idiosyncrasies of the smith who forged it, but what has most influence is the width of the blade and, related to this, the height of the ridge line along it. Blades with a high ridge-line are good when cutting through harder targets but against softer ones they fare poorly due to the absorption of energy. A high-ridged blade will lose about half of its cutting power when, for example, cutting the straw targets in suemono giri.
Comparatively, blades with a shallow ridge-line generally have a better cutting ability, although this can vary with the blade’s width. They are good at avoiding the energy absorption from softer straw targets and perform laudibly when cutting these. However, if the user gets his grip handling wrong such a blade can easily break. To give an example, the cutting ability of the blades made by Seki no Magoroku Kanemoto are said to be in the very top class of the best and finest swords, the saijo owazamono. One of the characteristics of the swords that he made was a shallow blade-ridge, meaning that they would pass through targets with ease. By comparison, the cutting edge of a dotanuki or that of the Mito school blades from the shin shinto period were objectively superior to a Kanemoto. However, when it comes to the cutting of fixed targets in suemono giri and dai giri the Kanemoto could slice through five bundles of straw whereas the former blades would peak at only three. This is down to the fact that blades with a high shinogi suffer considerably from the energy absorption caused by soft targets and proves that, even if the blade edge itself is exactly the same, the height of the ridge-line has an effect on a sword’s cutting power.
In short, this means that widening a blade and lowering the height of the shinogi will greatly improve its cutting ability.
On the other hand, when cutting bamboo, the blade’s cutting ability will not be affected much by a higher ridge-line. A higher shinogi improves the flexibility of the blade, making it more suitable to cut bamboo. By contrast, a blade with a shallow ridge-line will not have such great flexibility and is not recommended for this type of cut. If the cutting angle and grip manipulation is incorrect then the blade will often snap. This is best viewed along the same lines as using different blades to prepare different ingredients in the kitchen, such as using a cleaver to cut through harder ingredients and a vegetable knife to cut through vegetables etc.
Furthermore, the position of the shinogi line is also an important factor. It is not desirable for it to be too central along the width of the blade and, when considered from the perspective of the blade’s physical dynamics, being further towards the back of the blade (mine) will give a better cutting edge.’
2. Weight
A standard katana that would be easy to use will weigh between around 300 monme and 340 monme (between 1.1 kilograms and 1.3 kilograms) including the guard, hilt and fittings. Swords heavier than this would only be used by those with sufficiently prodigious physical strength.
At demonstrations of iaido one will sometimes see performers who make the length of their blade shake spasmodically when stopping it after a cut or when carrying out chiburi. The cause of this is the use of swords that are too heavy, and it is a bad habit to get into. One must be wary of heavier swords.
3. Curvature
The ideal curvature for a sword of two shaku and three sun (approximately 70 centimetres) is around five bu (approximately 1.5 centimetres). Swords with a greater or lesser curvature than this are not good for practical use in swordsmanship training.
4. Blade width
A blade that is around one sun (approximately 3 centimetres) at the base of the guard and tapers down to around eight bu (approximately 2.4 centimetres) at the monouchi will have a good balance. Just as with the curvature, blade widths that vary too greatly from these measurements are not suitable for training.
5. Dimensions of the tang
The dimensions of the blade’s tang control the overall balance of the sword and are an important factor to be aware of when selecting swords for use in training.
In general swords of the koto and shinto periods have relatively short tangs of around five sun (approximately 15 centimetres), although there are exceptions. The standard length for sword hilts (tsuka) is eight sun (approximately 24 centimetres) so if the tang is much shorter than this the blade may break at the tip of the tang when it cuts into a solid object.
If the hilt one is using is eight sun in length then a suitable tang should be seven sun. When a longer tang fits well into the hilt then its weight will be retained there and the blade will consequently become lighter, leading to a well balanced weapon.
If the tang is too short and this is putting too much weight on the blade then a good balance can still be achieved by inserting lead into the base of the hilt by the pommel.
It should be noted that in 1980, when Tameshigiri no Shinzui was published, the average height of Japanese men was 5ft 7ins and, at that time, Nakamura Sensei was yet to accept any Western students (I was the first in 1983). As he notes, blades longer than 2.4 shaku were not recommended for tameshigiri as those forged to the specifications set out here will easily bend if technique is incorrect. However, for someone of my height (arm/leg length ratio must also be taken account of) the correct length is 2.45 shaku (see image 2). Clearly a problem arises here if one wishes to practice tameshigiri. Given the average heights of the population today many would-be swordsmen and indeed swordswomen (both Japanese and non-Japanese) will be unable to find a sword that fits all of Nakamura Sensei’s criteria.
At a taikai in Gunma-ken in 1985 ( an annual event at the time) after performing well in the individual shizan (cutting) I opted to enter the Suemonogiri event in which the competitors attempt to cut vertically down through a stack of horizontally stacked straw mats. The chance of mistaking hassuji (correct blade angle) and tenouchi (correct grip) is much greater here. I was told in no uncertain terms, by both of my seniors- Suzuki Kunio and Sato Shimeo – that, given my technical level and the proportions of my blade, this was a very bad idea (my sword was a 2.45 blade purchased from Nakamura Sensei). Riding a wave of euphoria, I blithely ignored their advice and shortly after was rewarded with the sight of my sword bent at the monouchi to an angle of 45 degrees. I imagine the ghastly sensation this induced was similar to the feeling that might arise if I should wake in the morning to find my nose (or another appendage) had bent to a similar angle. This feeling was in no way reduced by the sight of Suzuki Sensei bending it back into shape with his hands and feet on the concrete ground!
In his later books Nakamura Sensei advocates the use of thin green bamboo, particularly for beginners, so that they can practice cutting until they have mastered basic technique and can attempt thicker targets without the fear of swords bending. This precaution is of course much more important now that the many taller practitioners are using swords longer than 2.4 shaku. At Fudokan we have successfully introduced the use of thick paper straws for this purpose (as pliant green bamboo is hard to find in the UK). This practice is actually more demanding than cutting tatami omote, as even slight deviation from good technique will result in the straw bending. However, as Nakamura Sensei stresses with regard to thin green bamboo, it is vital that the cuts are performed with full power and amplitude as if cutting a heavy target or a diminished cutting action develops.
The other approach is of course to make swords more robust. Nakamura Sensei often refers to jissento実戦刀 (real battle swords) to distinguish them from the blades he favoured that easily cut soft targets but which would likely chip, bend or fracture when contacting bone or the other materials present in ‘real’ targets. The chief feature of such swords is a thicker shinogi or ridge line. We will discuss the desirable specifications and cutting characteristics of longer swords in detail in part 3 of this article however the important thing to bear in mind here is that, however finely sharpened, such blades lack penetrating power when used on soft targets. Consequently jissento are rarely seen in the hands of Battodo practitioners. Soft targets (usually straw matting of some kind) have become ubiquitous in practice and tournaments alike. As I explained in chapter 5 of Kurikara (Blue Snake Books 2010) this has led to a steady move away from the sugata (shape) of a traditional katana towards a specialised ‘sports item’ with very little regard for the effects on balance, ‘wieldability’ and crucially, the cultivation of genuine martial swordsmanship. This regrettable development is laid out in the following image (Img. 3).