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Swords, Cutting and Military History

The Honourable Second: Forensic evidence of medieval kaishaku in seppuku

The Honourable Second: Forensic evidence of medieval kaishaku in seppuku

photo by jpellgen

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Within the practice of modern iaido and other Japanese sword arts, there remain katas which echo a solemn duty any samurai could be called on to perform. A duty which required the utmost in swordsmanship skill, precision and control.

I am speaking of  kaishaku, the act of being the assistant or “second” to a samurai who is committing ritual suicide by seppuku.  A samurai appointed to act as second was known as kaishakunin. While some translators have rendered this as “executioner”, traditionally the kaishakunin’s purpose was to relieve the suffering of the samurai committing seppuku by full or partial decapitation.  For reasons explained in the following section, most Japanese sword arts at one time trained their students in this act.  These practices survive today in specific kata, taught with a serious mind, requiring extreme focus and control by the student.


History and background of seppuku and kaishaku

The act of seppuku consisting of making two separate major cuts across the abdomen;  as such it was extremely painful.  So much so, the aid of a second was considered mandatory so the samurai would not disgrace themselves by being unable to finish.  Seppuku was used for a variety of reasons:  To prevent shameful capture (and torture) in battle;  To restore one’s honour if a crime or grievous error had been committed;  As a way of protesting the action of a superior;  and, in much later times, it was used as a judicial sentence for some crimes.

In early periods, a kaishakunin would wait for a signal from the samurai that they wished “assistance”; by historical tradition, this was signaled by the samurai bowing their head and exposing their neck.  In later, perhaps more merciful times, the doomed samurai would bend their head just in reaching for the knife, and their second would act.


Historic seppuku recreation

Posed 19th century photograph of seppuku by actors


The task of being kaishakunin was not an easy one.  While some clans did indeed have official kaishakunin —  samurai selected and retained for their skill with the sword —  there was always a possibility that bad fortune could force a samurai into taking the extreme measure of committing seppuku.  Thus, potentially any samurai could be called on to act as second for another.  In many cases the samurai committing seppuku would ask family members, comrades or friends to act as their second.

In acting as kaishakunin, the second was required to be extremely precise with their cut, wishing to prevent suffering and loss of honour.  On the other hand, the kaishakunin themselves could be disgraced by not fulfilling their role, by displaying poor cutting skills.   Considering the emotional stress a kaishakunin must be under, that the person they were acting as second for could potentially move (perhaps involuntarily) at any time, the difficulty of their task was monumental.  In addition to this, the custom was that the kaishakunin should not totally decapitate their primary — as only criminals had their heads completely removed.  The kaishaku was required cut through the neck vertebrae and vertebral artery and not much further.

This task was so difficult that Yamamoto Tsunetomo, the noted author of Hagakure, considered by some to the one of the defining volumes on what it was to be samurai, comments:

“From ages past it has been considered ill-omened by samurai to be requested as kaishaku. The reason for this is that one gains no fame even if the job is well done. And if by chance one should blunder, it becomes a lifetime disgrace.”  Hagakure

Thus samurai trained extensively in this ritual, preparing should they be called upon to fulfill the role.  By way of example, in the following video a practitioner demonstrates various forms of kaishaku taken from a range of koryu (older teachings, normally existing pre-modern era).  In many of the kata you’ll note an sudden stop to the main cut;  this displays the precision necessary to function as kaishakunin, as described above.



The act of kaishaku and forensic evidence

(Note that all the papers linked to in this section contain extensive forensic photographs, medical diagrams, measurement charts and other information.  Please refer to the papers if you wish to access this data)

One of the seminal forensic anthropological papers on this topic is: Note on the Technique of Decapitation in Medieval Japan,  by Dr. Morimoto Iwataro.  In his paper he discusses his examination of two sets of remains, an in particular their skulls, from the digs of  Muromachi period (14th century) ruins in Kamakura.   He notes that in each of these cases it is the neck vertebrae which are cut, with no other injuries present, indicating this was the cause of death.

In each of the two cases, Dr. Morimoto notes cuts into the 3rd or 4th cervical vertebrae, which would have severed the spinal nerve column and vertebrae artery, thus being a lethal cut:

“Judging from the shape and inclination of the injured surface, the sharp edge of the sword seems to have cut deep into the vertebral body in an oblique direction from the lower posterior right to the upper anterior left, and come to a full stop around the median line, associated with the secondary breakage at an area contiguous to the cut in the anterior left part of the vertebral body… …The present observations make it quite clear that the sword generally cuts deep into the cervical vertebral column and stops short within it. It is, however, highly possible that this halfway cut could put the convicted person quickly to death, because the sword would sever not only the spinal cord, but also the right vertebral and common carotid arteries. Old Japanese tradition said that the anterior skin of the neck of the convicted person should be left intact at the time of decapitation… …The author’s material indicates that the halfway-cut method of decapitation had been adopted not only in the recent Edo, but also in the medieval Muromachi period of Japan.”

In each case he also  finds evidence of a secondary cut from the front, which would have been made postmortem to remove the head.  The linked paper includes photographs of the remains and medical diagrams displaying cut positioning.


In another paper: A Decapitated Human Skull from Medieval Kamakura, Dr. Morimoto, joined by Hirata Kazuaki, examine another set of remains from the Murimachi period, which display cuts on the skull indicating severe “sharp force” wounding.  In a previous article we discussed definitions of sharp force wounds, which include:    Cut Marks:  shallow lines on the surface of bones;  Peeling or Shaving:  where bone fragments are peeled from a bone, indicating a strike at an angle;  Point Insertion:  a penetrating injury through the bone, often elongated or triangular;  Slot Fracture: a wide groove below which the bone is fractured;  a cut into but not through the bone;  and Chop Marks:  the complete cut of a bone.

In this case, analysis of cut and chop marks on the skull allowed them to deduce that the person was suffering multiple wounds, but that the lethal cut matched the description of a kaishakunin cut, as in the previous paper.  This being made from behind, oblique to the neck, severing but not cutting through the spinal column.  The paper’s authors go so far as to suggest:

“The decapitated male may have been a seriously wounded warrior, or samurai, who had given up all hope of living, and was then assisted in committing suicide, either by his wish, or an order as a result of an unavoidable circumstance. In Japan at that time, the execution of a samurai was considered a disgrace, thus suicide by sword was viewed as an honorable way of dying. After the identification of the head, which had been separated and taken away from the body, it was buried at the Yuigahama Cemetery in Kamakura. At any rate, the observations obtained clearly show that the sword for decapitation in the medieval Kamakura passed deep into the cervical vertebral column from the right rear, and yet came to a full stop within the bone after severing the spinal cord and the right vertebral artery, putting him to death.”


Finally, a dig at Osaka Castle uncovered remains believed to date from the 1614 Osaka Winter War.  The Winter Seige of Osaka was one of a series of battles launched by the Tokugawa shogunate against the Toyotomi clan, ending only in the total annihilation of that clan.  In their paper: Human skeletal remains from the Osaka castle site in Japan: metrics and weapon injuries, Nagaoka Tomohito and Abe Mikiko report examining two sets of remains — one male, one female — for both anthropological types and weapon damage.

On the male they found multiple wounds, including the indications of the partial decapitation used by kashakunin:

The second cervical vertebra shows two injuries. First, the right inferior articular process of the second cervical vertebra was injured in a direction from upper posterior to lower anterior (Figure 3d). Second, the decapitator seems to have cut deep into the right superior articular processes of the second cervical vertebra in a horizontal direction from right posterior to left anterior with the sharp edge of the sword(Figure 3e). The present observations make it quite clear that the sword cut deep into the articular process and stopped before the dens. These cuts could rapidly kill a person, because the sword would sever not only the spinal cord but also the right vertebral artery. In the Japanese way of decapitation by sword, the anterior skin of the neck of a convicted person should be left intact following decapitation by a halfway cut (Morimoto,1987; Morimoto and Hirata, 1992). The present observations suggest that the halfway cut method of decapitation had been adopted during the WinterSiege of Osaka


This then demonstrates the use of this technique spread over several centuries, and into the Edo Period.





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