kendo theory

Sankaku-ku (三角矩)

A few weeks ago, a guest of one of the young kendo teachers at my workplace was standing in front of the dojo mirror kamae-ing and looking at himself from different angles. I guess it is quite a common scene in many dojo with a mirror, be it Japan or elsewhere, but what got me interested was that this particular guest – already a quite young 5th dan – was someone who I had already read to be more serious than most are for his age kendo-wise. My interest piqued, I asked him what he was working on.

He admitted that he was having doubts about the super-straight kamae that he had been taught since he was a primary school student, and had decided to change it to a more “open” type, the type – which just so happens – I changed to myself a good 15-or-so years ago.

This topic, one I have briefly chatted about before, is about to get more detailed.

Yamaoka Tesshu (1836-88), was a kind of rennaisance man during his short lifetime: samurai, revolutionary, stateseman, artist, and of-course, swordsman… he was a man of many skills. Many books have been written about him and I am sure he needs no in-depth introduction here.

Instead, today I’d like to quote from one of his own writings on swordsmanship to start our discussion:



Kempo Sankaku-ku

Sankaku-ku, the triangular  relationship between the eyes, stomach, and sword-tip,  is something that must be studied. 

Swords should measure ten fist widths in length. Ten fist widths is about half of your height.  This is also about half of the distance between your hands when you extend both of your arms out to the sides, therefore, be sure to stretch out your entire body (and kamae) when facing an enemy.  In ancient times this teaching was called “Tenshin-shoden.” Sankaku-ku is based on this. 

The eyes, stomach, and sword-tip should work in unison when squaring up to an enemy. This is the teaching of Sankaku-ku.

Anybody who wishes to learn our style (Itto-Shoden Muto-ryu) must first study this teaching as the base princple above all else. Skill in swordsmanship, as with all things, begins first by obeying the principles. Only by doing so you will learn the underlying theory. It is essential to faithfully study sankaku-ku. You cannot discover the deepest secrets (of swordsmanship) without doing so. Effort… effort…. 

– Yamaoka Tesshu, March 30th Meiji 16 (1883)

The above quote I found online, but I have an almost identical version in a book at home. I just copied and pasted for convenience. It has been loosely translated, and at times I have re-arranged the sentences. I must admit it was a bit difficult in places! Note that the length of “ten fists width” depends on how exactly you measure. Some online sources said it was the distance between the index and pinky fingers on a closed fist. Note also that another book I referenced below provides a modern translation (by Omori Sogen) and a further interpretation of what is written above. It ascribes a dual meaning of the term, the first a three year severe shugyo process of learning the basics of something (in our case swordsmanship), as well as the length of the sword and the triangle itself.


Although the above Japanese is a little bit confusing (and the translation even more so!) the teaching is quite clear: be sure and learn how to kamae properly.

Obviously, as I’ve mentioned a few times here on kenshi 24/7 before, and you’ve probably worked out for yourself, a wonky kamae leads to wonky kendo, so it is best to spend a lot of time working on and improving it, as well as allowing it to evolve over time, like the young godan mentioned at the start of this article.

One way to help improve kamae, I suggest, is to read-up on kendo theory. While very easy to do in Japanese, this can be hard in other languages. Hence, today’s article.


Yamaoka Tesshu’s “Sankaku-ku” could be prosaically translated into English as “carpenters square” and is pretty easy to understand: it refers to a triangular connection (or zone) between the eyes, sword tip, and stomach while in kamae, and how these three must constantly act as “one,” be “in unison,” or stay “connected.”

Stomach here, in my interpretation, refers not so much to your tanden, or area where ki or “energy” is said to accumulate in your body, but is more about keeping your hands (well, left hand in particular) and stomach “connected.“

Needless to say, this theoretically triangular zone or connection should never be broken, for example lifting your left hand up in a protective sampo-mamori posture, striking degote with the tip of the shinai whilst ducking your head away and not looking, or turning your back to your opponent and fleeing after a gyaku-dou strike.

So, at this point here I’d like to introduce the “open type” of kamae mentioned at the top of the article. As you can guess, this has oft been referred to in tandem with the sankaku-ku principle.

I planned to start by showing some diagrams from an unpublished manuscript by the late Matsumoto Toshio sensei (hanshi kyudan), but I can’t for the life of me find it. Luckily, at least some of the manuscript was serialised in one of the kendo magazines, and I was able to discover a handful of the pictures online. At any rate, I am able to share a small handful of his diagrams, of varying quality (sorry).You might have seen them before:

In kendo, we kamae with our right foot forward, and place our right hand in front of the left on the shinai. For the first ten or so years of my kendo career I took this position and then, incredible as it is to think about it now, I tried to completely straighten up my hips and shoulders so that I would be dead straight square-on to my opponent. Needless to say, I struggled to force myself into this strange position. I guess I was not and am not the only person.

I long ago gave up trying to be dead straight and the more I did so the more I saw that many, not one or two or even three, but many many sensei over here don’t either. “They are old and can’t stand properly” one young guy once said to me. Of course, that was simple a comment by a as-yet immature kenshi:  they had just taken a more “natural” posture. 

What finally made me decide to give up the dead-straight kamae and argue for it if anybody tried to “fix” it was, however, my kenjutsu background: I knew the theory. 

The kamae itself

In the kamae itself the left foot may be slightly splayed out, which is perfectly fine. The left fist moves slightly to the left, with the extension of the sword tip aimed at the opponents left side (left eye when not moving). What becomes the “centre” of the body is somewhere in the vicinity of the right thumb’s knuckle.  

All things being equal, it follows that it is almost certainly faster to strike someone on a dead straight line from a super straight kamae. And that’s why the style has become so common in modern kendo (which has also arguably helped diminish waza variation in shiai nowadays = debana men, degote, hiki-waza). But, personally, I don’t care about speed so much, and I find kendo theory super interesting, so here we are!

From this kamae, seme-ai becomes different. It is not about speed, but rather, as Takano Sasaburo said:


“In sankaku-ku kamae use the opponents attack to strike them back. You must constantly pressure them and feel like you are going to strike first. This is called victory through the opponent.“


This is only part of a larger quote but, basically, what Takano says is that when in this kamae you shouldn’t fear about being struck as it is easy to stop any attack or use the opponents strike to defeat them. Your right kote and dou are not open and so cannot be struck (if you keep kamae) and it’s a simple matter to execute suriage or kaeshi waza from the kamae (as you are already in position).

Takano Sasaburo (l) and Ogawa Kinnosuke (r)

Striking a “straight” men down the centre becomes an exercise not in speed (as striking directly from the kamae would result in a little bit of a yoko-men), but in seme: pushing or pressing down on top of the opponents shinai with your right hand (seme-te) you not only kill your opponents sword (ken-o-korosu) but cause them to freeze (itsuku, ki-o-korosu); or perhaps, reacting to your seme, they attempt to strike back at you, but that’s ok because you are also mentally prepared to execute a debana, kaeshi or suriage waza (waza o korosu); if they move back or attempt to block you, step in deeper or modify where you intend to strike… which you can do because you are mentally (and by this time physically) in control. 

As pressuring your opponent becomes your modus operandi rather than speed a number of things happen: waza variation will increase; multiple strikes reduced; wasted attacks (eventually…) disappear; you begin to focus on reading your opponent (rather than being selfish); strategic depth increases; and eventually (hopefully) a more dignified kendo style will appear.

Of course, reading Yamaoka’s words and looking at the illustrations you could easily imagine his sankaku-ku to refer to the dead straight kamae as well. That’s cool… he didn’t actually expand much on it in the written word anyway. I am sure you could easily take the idea and work with it, in fact, I am sure some have.  

An old idea re-fashioned for modern kendo

Also, it is important to note that the type of sparring in bogu with shinai that he did is NOT the same as we do today – kendo has evolved into something much more athletic with speedier, lighter strikes, with a longer shinai… all of which would be anathema to Yamaoka. His sparring style would have been informed by the theory embedded in the kata he practised and taught.

For me personally, I enjoy taking some of these theories and applying them to modern kendo (via my kenjutsu training of course).

Although today you got my interpretation on Yamaoka’s ideas, you can see that kenshi before me did the same, starting with Takano, continuing to Matsumoto, and there are plenty of people researching even today, including the young godan in the mirror at the top of this piece.


This is not a full list of sources.

  • 一刀正伝無刀流劍道書。非売品。発行不明。
  • 剣法無刀流。塚本常雄。1968年発行。
  • 山岡鉄舟・剣善話。高野澄訳。1971年発行。
  • 剣道事典・技術と文化の歴史。中村民雄。1994年発行
  • 百回稽古。小川忠太郎。2000発行

By George

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2 replies on “Sankaku-ku (三角矩)”

Yet again an interesting, well written piece. Thank you so much for your time and effort mate!

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