u/GunsenHistory

I decided to go back to the archeometallurgical literature I own to do some brief analysis and make it public. There is something fascinating about the steel of antique swords. The patterns we can appreciate are rarely seen with modern, industrial-grade steels, and those who collect nihonto or wootz blades will probably understand me.

However, I am posting this review of the available data for a more mundane reason, which is to close the divide between the "perceived" technology of these tools and the real, archaeometallurgical data. Understanding the limitations of the period steel can bring us closer to understanding how these tools were used in their historical context. In my opinion, modern practitioners and reviewers do not really appreciate the difference between a state-of-the-art Albion and a 500-year-old Solingen blade. And every time I hear collectors or practitioners talking about historical metallurgy, there is so much confusion about the steel and heat treatment used.

So here we have it: a total of 84 blades, a few daggers but mostly swords, from the late 11th century to the 17th century. First, to understand these data, some methodological notes. This part can be skipped for those interested in the results.

Methodological Notes

The primary literature used to inform these graphs was "The Sword and the Crucible" by Alan Williams and "Technology of Sword Blades from the La Tène Period to the Early Modern Age The case of what is now Poland" by Grzegorz Żabiński, and a handful of other papers. The book of Williams is probably the most complete on the subject, and a must-read for those interested. However, some of the analyses are very brief, no more than 100 words per sample. I have excluded the pre-11th century blades from both books. The analysis was divided into total and "post 1300", to capture the late medieval and early modern period. The 1300 period was chosen since Zabinski gives very broad spans, such as 1350- post 1400; therefore, any other time cut might have excluded some blades from the Renaissance.

A. Composition

Both Williams and Zabinski have their own categorisation to determine the sword type and the construction method, and I loosely followed it with some caveats. For example, Williams divides the 10th to 17th century blades as follows in order of quality :

1. IIA swords apparently made of one single piece of steel
2. IIB swords made out of several pieces of steel
3. IIC swords made out of several pieces of steel but not hardened
4. III swords with hardened steel edges and an iron core
5. IV swords with unhardened steel edges (cores undetermined)

However, there are some challenges in applying this classification. In his IIA samples, IIA.5, we read:

>A half-section was removed; the microstructure shows a fairly homogenous steel, which had been folded and forged into shape, then hardened by slack-quenching and tempering. The three higher-C% bands have an average hardness of 437 VPH; the two lower-C% bands one of 253 VPH.

So the steel is defined as fairly homogenous - yet containing different bands of low and high carbon steel. Was it really one single piece of steel? No further details are given on the carbon gradient. Further, in II.A.8, 9, 10 he cites three different rapiers, which were made by folding bloomery steel so that

>the carbon content varied between 0.2% (in the core) and 0.6–0.8% (near the edges and surfaces).

Perhaps one single ingot, but far from being homogeneous. Therefore, the threshold between IIA and IIB feels arbitrary at times. The same rapiers have been analysed in a paper by Garner and one by Merico, and show either different steels used in combination or even wrought iron pieces in the section of the ricasso. Again, not really a proxy for "homogeneous". Zabinski extends the classification of Williams, but loses its "quality scale". In his typology, carburised iron blades end up as subsets of Williams' IIA type, which becomes rather confusing. Therefore, to simplify the composition, the following was used:

• Homogenous steel: "relatively" homogenous steel, utilising one single ingot without significant spread in carbon content
• Banded steel: when the microstructure explicitly states alternating layers of different carbon content
• Laminated: Welded steel edges to a body of iron/low carbon steel.
• Carburised edges: blades with low-carbon steel/iron cores and steel edges

They are partially ranked by quality, but with some caveats; a lot of those samples did not give accurate measures of the carbon content. The line between banded and homogenous steel is very much based on the paper's way of describing the steel billet. So there might be some overlap: the presence of alternating layers is observed in virtually all micrographs shown, therefore, how much "homogeneous" something can be is very much arbitrary.

B.Hardening

Next is the hardening method. This is based on the difference of the microstructure observed in the egdes/flat (outer layer) as opposed to the core/centre. Some observations had to be dropped, as the core was unknown in Williams sample. However, in some examples, he describes what could be seen as a gradient of hardness and/or carbon content approaching the core, therefore this can be a sign of laminated/carburised edge structure which will inherently yield a partial heat treatment.

The categories used are:

• Full quench and temper: the resulting microstructure is dominated by tempered martensite, both in the edge and core
• Hardened with ductile core: microstructure showing tempered martensite/bainitie or harder phases on the outside, ferrite and pearlite (unhardened) phases on the inside. This category includes the very popular "slack quenching" or "time quenching" techniques used in the period.
• Unhardened: quite self-explanatory, including pearlitic edges and/or air-cooled blades
• Other: all blades that either had a partial quench (only 2/3 of the blade hardened) or failed ones (overtempered martensite)

A big caveat of this analysis is that a micrograph can only give us a snapshot of the blade. Many of these blades could only be sampled at one section. In cases where multiple samples were analysed, such as the aforementioned rapiers, it was clear how the ricasso and the blade had different compositions and hardening.

C.Hardening measurements

All the hardening measures were given in Vickers hardness. Multiple studies reported either different ranges or an average value. These were sourced for the core and the edge. The values used, when available, were the reported averages. Otherwise, the average between the minimum and the maximum value was considered. For the core, either the reported average or the minimum value was considered, as the presence of a ductile phase will dictate the mechanical behaviour of the blade.

Results

The results are very interesting. When looking at the amount of blades showing banded steel and composite (either laminated or carburised edges) is almost the totality of the sample: 92.2% overall and 90% for the Late medieval period. Even considering the more "homogeneous" versus the clearly composite blades, the majority show low carbon steel cores (57% and 52%, respectively). This is a very different situation from the so-called "monosteel" factoid I keep hearing about when it comes to medieval swords.

https://preview.redd.it/wf36t3r55hbh1.png?width=708&format=png&auto=webp&s=2455a2c9433cae500dff79371a9ef2b8eec3ee9d

https://preview.redd.it/qyz505j95hbh1.png?width=708&format=png&auto=webp&s=c9594fabd72d57e68192c52a4bbfae61d5702fe6

The result is consistent in the difference between the edge hardness and the core. Even if some blades sported martensite in the core, there were many instances of ferrite/pearlite zones embedded within. There are also notably fewer observations (48 blades), but high hardness values are almost nonexistent. The average for core hardness was 172 for the total sample and 170 for the late medieval swords.

https://preview.redd.it/l06uuftb5hbh1.png?width=1303&format=png&auto=webp&s=1f380f6c6bfc89181a84bbc86c87b70d063c9138

Edge hardness is also very low, compared to the modern standard. The average blade is around 438 or 44 HRC. There are some properly hardened blades, but measures above 520-580 are almost nonexistent among the 74 blades showing edge hardness. It is notable that even well-made blades, such as one signed Passau, did not even reach 400 Vickers.

https://preview.redd.it/4s4m637d5hbh1.png?width=827&format=png&auto=webp&s=4e40fee200834fc9c133a2bcc5f9402ec098be36

The overall assessment holds with the type of hardening, informed by the microstructure. Only a mere 5.2% and 6.7% show something akin to a full quench and temper (with relatively low hardness by modern standards). The vast majority of the sample has hardened edges and ductile cores. More than 90% of the blades had unhardened or partially hardened cores (if these were hardened at all in the first place).

https://preview.redd.it/u14cyybg6hbh1.png?width=760&format=png&auto=webp&s=00678f3329afb6a5f98e7221c480afd914b4573e

https://preview.redd.it/8eof10gh6hbh1.png?width=760&format=png&auto=webp&s=bb43815814079cc73f15b9e7e26bf623db1192ac

Most blades were quenched by slack quenching, or had composite billets with zones in the core that would not harden anyway due to low carbon. Not really the equivalent of what I would call "spring temper", "spring steel" or anything similar. And most importantly, period steel was not alloyed; therefore, the hardenability of the blade was relatively low. Thin blades, such as those found in rapiers, could harden at the tip, but anything substantially thicker and/or wider would have formed complex phases of martensite, bainite, pearlite and ferrite. In fact, many longswords in the sample feature this type of hardening.

Conclusion

Some notes: the sample by Zabinski includes blades found and/or located in Poland - this does not imply that those blades were made locally. A few blades are signed from Passau, and the possibility of trade between western European centre of arms is discussed in the book. There are blades from Spain (Toledo), Germany (Solingen), English swords, Italian swords from Brescia and so on. The sample is rich and widely distributed across Europe, and most of these blades were well crafted and functional tools. A few were corroded, and there are naturally some missing data, especially for the material found in the core. Not to mention that I did the sample review, and I might have missed some data entry. Are these representative of late medieval blades? I think so, and this is the best we have in terms of evidence. Is it complete? Probably not. But I do not expect any additional information to change the picture at large.

This might come as a shocker for someone who has never opened a book and believes that European blades were by far and large spring "mono" steel blades. In fact, it is a mantra I hear every other day. But experts within this field, well familiar with the literature, have been saying this for a while [1](https://www.youtube.com/live/4heLPFFaLaU?si=0he7kB9ms3ZFlXXT&t=5700), [2](https://www.youtube.com/live/5jrL5mvf4V8?si=vbE1Fbfo6ekhJdKB&t=4260), [3](https://youtu.be/5djVkOgu8vs?si=YaGbB99vBU\_\_awKS).

Does it mean these blades were badly crafted? No, they were not. Some were exceptional pieces of technology for the period. Yet these are swords that would likely take a set on a bad cut, and get severe edge rolls during use. And I feel practitioners, collectors and enthusiasts should start to learn properly how these tools would have behaved under stress, since modern tools are far more forgiving and durable than anything made 500 years ago.

References:
Williams, A. (2012). The sword and the crucible: A history of the metallurgy of European swords up to the 16th century. Brill.

Żabiński, G., Stępiński, J., & Biborski, M. (2014). Technology of sword blades from the La Tène period to the early modern age: The case of what is now Poland. Archaeopress Archaeology.

Fajfar, P., Medved, J., Klančnik, G., Lazar, T., Nečemer, M., & Mrvar, P. (2013). Characterization of a messer—The late-medieval single-edged sword of Central Europe. Materials Characterization, 86, 232–241.

Merico, P., Faccoli, M., Gotti, R., & Cornacchia, G. (2024). Archaeometallurgical investigation of a fragment from a medieval sword blade. Metallography, Microstructure, and Analysis, 13, 257–271.

Merico, P., Faccoli, M., Gotti, R., & Cornacchia, G. (2024). Archaeometallurgical study of a 16th–17th century "rapier" sword manufactured in Caino (Northern Italy). Metallurgical and Materials Transactions B, 55(2), 782–798

Tonelli, G., Faccoli, M., Gotti, R., Roberti, R., & Cornacchia, G. (2016). Archaeometallurgical investigation of a Renaissance falchion sword manufactured in Caino (Northern Italy). JOM, 68, 2233–2249

Lantos, S., et al. (2025). Unburied Mohács: New research results on the battles of 1526 and 1687. Budapest: Hungarian National Museum

Gener, Marc. (2009). Metallographic study of some 17th and 18th c, European sword (rapier) blades.

Mori, Carolina & Ghiara, Giorgia & De Montis, Paolo & Piccardo, P. & Gatta, Giacomo & Trasatti, Stefano. (2021). Archaeometallurgical Analyses on Two Renaissance Swords from the “Luigi Marzoli” Museum in Brescia: Manufacturing and Provenance. Heritage. 4. 1269-1283. 10.3390/heritage4030069.

Žákovský, P., Cymbalak, T., Hošek, J., & Dejmal, M. (2017). Archaeological find of a late medieval long sword from Prague – Nové Město/New Town. Přehled výzkumů, 58(2), 141–182.

Based on several interactions I had over the years, I wanted to share a bit of a rambling post on Japanese swords, and their use in historical battles.

This topic was brought up again in a recent Matt Easton video. As for the subject of the video, which discussed which swords will be useless against plate armor, and to some extent armor in general, I find the choice of including "all Japanese swords" odd, and the arguments presented very lacking. The main reason for this post is to address once again the eternal, everlasting misconceptions people have on Japanese swords, their use and their durability.

Matt's argument rests on two main points. One, is the "material" issue. He claims Japanese swords are brittle at the edge, and soft at the spine which translates as the tip, and edges more likely to break off, and the sword to bend when used to attempt bypassing armor gaps. This implies that Japanese swords overall were unsuitable to sustain clashes with armor, or any other hard surface (including other swords).

This is a recurring idea that shows up systematically every time Japanese swords are discussed, despite the amount of literature, scientific and historical, to dismiss it.

The claim originates from the hardness level of Japanese swords. In material science, high hardness, in modern steel, correlates with brittle mode of failure. It also correlates with high strength, and low toughness. In layman terms, a very high hardness, high strength but low toughness material will resist to wear of the surface, localized plastic deformation, does require a lot of force (for a given cross section) to deform, and when it does it absorbs little energy and cracks (low elongation).

Now, the hardness value alone is not sufficient to prove all of the above, especially considering the pre-modern context of historical steels.

There are some interesting findings from a Japanese sword made 500 years ago. In the paper published by Kwak et al, they performed hardness, micro-tensile and micro fracture tests on two different antique swords. In the oldest of the two, they found that even with high hardness, the micromechanical testing study indicates that in the sharp-edge regions, strength and fracture toughness are simultaneously enhanced by the presence of fine pearlite.

Further, none of these settings are considering the effect of geometry. Edge geometry plays a fundamental role in terms of failure, and reinforced tips/edges with appleseed geometry are much more resilient against impact compared to finer ones. Here is a video showing impact testing on a modern, 1084 knife blade, hardened and tempered at 64HRc vs one hardened and tempered at 57 HRc-62 HRC. Using different practical impact tests, despite the anecdotal evidence, you can see that the harder edge performs much better than the softer one. And that is mostly governed by edge geometry and high strength, in fact at more acute edge angles, the aforementioned relationship is valid: the harder edge cracks while the softer one rolls.

As for the softer spine, we are again not considering the effect of geometry. Most Japanese swords, as a matter of fact, are very thick and rigid. Ignoring the fact that with pre-modern steel, you will not have a completely through hardened sword, and that most historical blades have ductile cores of wrought iron/low carbon steel, Japanese swords are much stiffer on average than many European blades such as rapiers or longsword designs. This alone should reframe the whole argument because no, Japanese swords are not easier to bend, quite the opposite, and when it happens they deform rather than break. I struggle to see how this can be a bad design for dealing with armor.

Finally, the second point rests on blade geometry and the shape of the tip. Ironically, in his video he is showing an elongated, slender tip geometry known as ōkissaki. With a regular, short Japanese style tip, I would agree that it will be very hard to successfully bypass mail. However, this is an entirely different geometry. We know some of those tips were reinforced, and the slender acute point definitely gives them a good chance to burst into mail rings. I think discarding their effectiveness without testing is not a great argument, especially since those tips were used against armor in various other contexts.

Overall, while Japanese swords did not transition into estocs, there was a change in blade designs from the 14th century which accounted for dealing with armor. Leaving aside the topic of the video, and extending the context as a general "swords use against armor", there is a text known as Kenpō Ryakki which talks about fighting in armor with swords.

It talks about striking with full force with a sword against hands and limbs to break bones. In a Chinese text written by Chen Zongyou, Exposition of the Original Shaolin Staff Method, it is written that

>Japanese swords, and the tie bian, they are the same

the tie bian being a mace. And the main strategy suggested is to aim for the gap and to thrust with your blade. That is also found in other later period manuals; from the Kōdōkan Jūdō Official Bulletin "Yūkō no Katsudō," Volume 6, Number 6: Jūdō Anecdotes from the Atsukaishin-ryū, based on the Noda Family Documents, we can read that:

>When the body is firmly protected by armor, it cannot be cut, so thrusting is preferable.

Most of the gaps identified in the Japanese armor system are also quite universal: the armpit, the face, through the gap in the skirt armor to the lower abdomen, the feet, the hands.

Some of these places, such as the groin and the armpit, could be shielded by mail patches, and other flexible armor elements. The tip of these swords was in a sense expected to deal with such armor. There is definitely a correlation between extension of flexible armor to cover the gaps, and ōkissaki/shobu zukuri geometries.

To conclude, I do not think that Japanese katana and Japanese swords in general are completely useless against heavy armor. The arguments on steel durability are exaggerated and overly emphasised on Japanese swords, while the development of dedicated geometries is often ignored.