When studying Aikido classes often start with ikkyo, which is the first technique. Beginners and experts practice together, and it is thought that you can continue to improve your performance no matter how far along you are in study, by continuing to study the very basics. 

For swords the topic is sugata, and there are some problems with how books address it.


What book study says is true but it applies to archetypes. People make two mistakes when reading about archetypes and then trying to put the knowledge into play.

  1. Archetypes are most typical or most distinct examples of a particular school or period. They are not averages, and examples under study often stray from the archetypes in several ways. Thus, dismissing an example because it does not match the archetype which is documented in a book is not always a correct conclusion.
  2. They do not think to adjust for the effects of suriage.

I’ve discussed archetypes before, but suriage is really something to keep in mind because it gives us only a partial vision of how the sword was originally made. 

So the remainder of the blade we’re looking at is abbreviated and we don’t know what the original length was and so what section of a curve we’re looking at in many cases. A very, very long blade cannot be made so that a 70cm suriage blade has a deep curve left in it. The reasons for this is that if the blade is both long and deeply curved it will start to approximate half of a circle and not be a useful weapon. 

We can’t even look at rare ubu examples of a smith’s work and entirely understand what his target would have been on his biggest blades, because the ones left ubu were more likely to be of a non-awkward length. 

There are some blades in shrines that are 120cm to 150cm and so forth for use in the Nanbokucho period. Take them out of the shrine and someone would have cut those down for use at a normal length. So a lot of what we look at when suriage, we can’t just map it to the average length leftover of the ubu ones but consider that it could be like that or on the longer side. 

This leads us right into the rookie mistake, where they see a suriage Kamakura blade and misidentify it as shinto or believe that it is a disguised shinto blade because of the sugata not matching a deep koshi-zori or torii-zori shape. It may have been just extra long and so the curve has to be more gradual, and when it’s cut down the remainder appears unusually straight for the period.

Consider the following examples.

From left to right these are:

  1. Ubu Heian period Tachi by the Gojo school.
  2. Suriage but mei-intact middle Kamakura tachi by Osafune Mitsutada.
  3. O-suriage late Kamakura katana by the Aoe school.
  4. O-suriage Early Nanbokucho katana by Rai Kunimitsu
  5. O-suriage Middle Nanbokucho katana by Osafune Yoshikage

We can see over time a general design change where widening of the sugata first begins in general and then taper is lost as the kissaki increases in length. The width of a typical middle Nanbokucho period at the top of the blade has to remain quite wide in order to balance the length of the kissaki and prevent it from becoming misproportioned. 

The result is a wider blade in general, but less difference between the top and bottom of the blade. 

The Rai Kunimitsu katana seems fairly straight when set with this crowd but I think this is a factor of the blade being made quite long and the deepest part of the curve being cut when the blade was shortened.

The relative deepness of the curve in the middle Aoe blade I think reflects that it is fairly close to ubu in shape and so we see most of this curve saved after suriage.  

The examples that remain as tachi though are those that we can compare most closely to the archetypes.

Furthermore the ubu Gojo on the far left not only matches the archetype, it is the archetype of a Heian period blade in all ways. 

For this reason also, depth of a curve is difficult to use to gauge period because the more suriage it is, the less depth we have so in general the sori measurement needs to be taken with a big grain of salt when making conclusions. 


All of that said, when you look at the upper part of the comparison images definitely we can make a mapping there to what we know from archetypes and the relative ages of the blades match quite perfectly. The one exception is that the middle Kamakura example does not have ikubi kissaki, but that in general is a rare feature though it is considered achetypal for the time period. 

But we can definitely see from looking at o-kissaki and ko-kissaki examples that this is a very nice tell in the kantei game. An overall impression of the shape of the blade, lightly built blades with suriage or without will tend toward being earlier and heavier blades or those that look awkward after suriage are implying the length and size of Nanbokucho period works.

The late Kamakura works though, even after suriage seem to often retain the magic of a perfect curve and sugata as is seen in the Aoe example. 

What I am left with is more of an impression of what the curve and shape tells you vs. trying to measure every aspect of it, because we have to deal with the effects of suriage without knowing if we’re looking at the upper half of a massive tachi or the upper 90% of a blade that got cut just above the mei.

So just keep that in mind, that jumping directly to the rules of an archetype will only apply if the blade is ubu, or close to ubu. Once a substantial portion is lost you will need to try to extend the blade in your mind to try to guess what it originally looked like, and then use that imagined sugata to match against the archetype.