The katana existed centuries before the Japanese started wearing (effective) armor with any regularity. 'Heavy' armor, in Japan at least, did not start gaining popularity until sometime in the 14th century (or possibly late 13th, I don't have any of my source materials on hand at the moment), which was, incidently, around the first time the Japanese had any meaningful contact with the European nations. If the katana had indeed been designed for use against better protective armor than Japanese warfare had been previously acustomed to, then there would more than likely have been radical changes in the design of the blade in order to adapt to new advances in personal protection (in this case, better armor). Besides the fact that a single bladed weapon which was not designed for thrusting attacks is definately a suboptimal choice for combating armor, the fact that the basic design of the katana has changed little over its (very long) history suggests that no such evolution was necissary, and thus, not designed for use against armor.

Mind you, I could be horribly, horribly wrong, and if so, a link or two to redeem my groggy sense of history would be much appreciated.

OMG!! Sorry for going OT here guys, but I just read the link about the sword robbers and this happened in the city I live in!!

Shadowrun is becomming more real every day!

That is true of many Western European swords throughout the Middle Ages. Already from 500 to 0 BCE, a significant portion of Celtic swords had steel edges and an iron center. Throughout the early Middle Ages, swords with iron centers and steel edges welded on or case-carburized were common, and so was partial and slack-quenching. A sword recovered from the Mary Rose, which sank in 1545, had forge-welded steel edges around an iron center, and had been fully quenched for a hardness of up to 590 VPH at the edge (average 507 VPH), with the center ranging down from 280 VPH.

And at a brief glance at various sites and articles discussing how katanas were made, I have to agree with Darkness that it doesn't seem likely many medieval katanas would have had steel of different composition (pre-quenching) along the edge and the spine. I could be very wrong about this, though.

I agree that in certain conditions such a sword could be used to cut through leather armor in combat, but whether I can agree with the "medium armours" bit depends on your definition of these. Cutting through cold-worked copper or bronze or any kind of steel (ie. not pure iron) armor is not going to happen, but it just might work against hardened leather and other non-metallic rigid armors.

Methods varied from smith to smith, but it was not uncommon for japanese smiths to use multiple layers (laminate) of steel with different compositions. A good example of this is the "soshu" (spelling?) style, which used 7 different layers.

Heavy armor came and went with the times and the kinds of problems facing the bugei of any particular era. I just deleted a long and very dry paragraph talking about the types of armor that were used and when. Instead of that, I'll just list the prevalent styles:

4th-6th Centuries: 'Tanko' Armor - solid metal plate construction.
7th-9th Centuries: 'Keiko' Armor - hardened leather or bronze (much rarer) scale construction.
9th-12th Centuries: O-Yoroi - hardened leather scale with additional hardened leather fronespiece on the chest, occasionally with metal plate backing on the torso. This is the first armor to make use of kote (sleeves), most of which are cloth impregnated with mail around the forearm, with solid metal plates on the upper arm, a style known as 'bishamon-gote'. This armor was designed for mounted archers, as this was the primary calling for the bugei of this era. Kinda a bitch to move in on the ground, but not so much of a bitch it impairs fighting. It's just basically uncomfortable.
12th Centuries+: Do-Maru, Haramaki-do, etc. 'Scale construction' armor as we know it now started in this period. Rank and file soldiers would generally have hardened leather scale, officers would have steel scale. It's worth noting that despite being 'scale armor', it's nowhere near as loose as scale-on-leather as Europe and the Middle East had it. The scales were laced tightly together and then laquered, forming 'boards' of armor. This era also marked the rise of the use of haidate (upper leg armor); generally haidate plates were made of metal, not leather.
14th Century: Mail impregnation becomes the norm for all joints and non-plated areas such as the arms, armpits, et cetera. Suneate (lower-leg guards) become much more common. These are almost always made of steel plates with a 'coat-of-plates' style knee guard. There's only two types of suneate that don't use metal, and one of those was a coat-of-plates style guard, and the other is made of hardened leather and was fairly rare.
15th Century+: As a rule of thumb, metal becomes more common, solid-construction breastplate style armor becomes more common, mail becomes heavier, and then you get to the Edo period and everything gets frilly and generally worthless for warfare.

So. What does this tell us? It tells us that the Japanese had some pretty disparate armor that was, in general, pretty good at stopping weaponry. It also explains why most schools of swordsmanship from the era tried to make cuts at joints, straps, or through gapping in the armor. Their armor was under no circumstances harder to get through than plate - though some of the 15th and 16th century suits came fairly close. However, it was far from 'weak' armor, as the armor is much tougher to cut through than many equivalent types of hardened leather from surrounding countries. (You're probably going to have to trust me on that one, unless you have somewhere you can go to actually physically look at and pick up suits of hon kozane armor. They're very hard-plate-shell like, due to the stiffness of the 'boards' of armor).

Actually, the katana has undergone some fairly decent changes over time, but most of the are with regards to construction style, not shape. In general it became shorter and sharper over time (from the time when they were intended as a mounted weapon to an all-purpose weapon). This is where the real 'mythic' nature of the Katana came from - it's a study in doing more with less. Since Japan didn't have the ten tons of iron to toss around that Europe did, artisans spent more time and effort on individual weapons and suits of metal armor than most European counterparts did, though High Gothic armor and weapons would certainly give them a run for their money. Most of the changes in the katana were in terms of refining forging techniques, not changing the shape of the blade. The only blade-shape change was to reduce the level of curvature found in earlier tachi to the more slight curve in the katana.

As to thrusting, every historical Japanese school of swordplay that we know about (via historical texts, not modern inheritants) used thrusts. Part of the major difference between Europe and Japan with regards to sword style and thrusting is that the Japanese did a lot less of it in general, due to a lack of shields and the fact that the Katana is a two-handed weapon. In general, cultures that made heavy use of shields had more thrusts in their styles than ones that didn't use shields as much - or at least use shields in formation. At least as far as I know - that isn't fact so much as supposition from what I know about various cultures.

In summation, I'm not saying your ideas are wrong in nature, I'm saying they're wrong in degree. There's no way a katana would fare decently well against European plate armors, but they could do a decent job against leather, coat of plates, mail or such similar armors.

Austere Emancipator said:

How I respond to this depends entirely on how I read your meaning. If you mean cutting through cold-worked copper or bronze in terms of PLATES wouldn't happen, you're dead on the money. If you mean small plates, scales, or mail, I regret to inform you that you're incorrect. The attacks taught to soldiers relied primarily on cutting through mail and small-plate areas of armor much more than through the leather portions. Cutting attacks were directed at arms, sides of legs, shoulders, neck and hips - all of which were generally protected by metal in scale, small-plate or mail fashion - and thrusts were the preferred method of defeating torso, thigh and stomach protection.

If you're talking about hard plates though, yes. But by the same token, European swords couldn't defeat later plate armors dead-on, either, and tactics had to be revised to attack joints, joining straps, or just to straight bludgeon the wearer unconscious. Some of the more amusing manuals I've seen involve two guys in plate, with the tactics of both parties seeming to be 'wrestle the other dude to the ground and stab him through the face with your knife.'

I would love to see that in action, to see a sword actually cut through 1.5+mm thick cold-worked steel (or any other 100VPH+ metal, either in small plates or as a mesh of wire of that gauge) on a single slashing attack. I have never witnessed or heard of a sword managing anything like that, nor can I even remember references to using cutting attacks (connect-and-draw as opposed to simply hacking) against opponents in metal armor anywhere. If you've got any references, I am very interested in seeing them.

As far as I can tell, sword attacks against metal armor weren't meant to cut through those parts of the armor, but to hack or bash through them -- and this I know can be done with certain swords against most such forms of metal armor (excluding plate armor, and may be unfeasibly difficult against some other types as well). But, again, I could be wrong and I'd appreciate any references.

Absolutely. The point of my message was to say that it can't be done with any swords, not just Japanese ones.

16 gauge wire is 1.6mm in outer diameter, and according to several articles (like this) that's quite average for mail hauberks -- though admittedly the actual thickness of the ring in the direction of impact might have been slightly smaller because the rings were usually flattened.

As you know, this kind of testing can be totally off-base depending on the exact construction of the mail -- was the mail riveted or alternating riveted and punched rings, or even (gasp) butted mail? Were the rings flattened? Were the rivets round or triangular? What kind of iron/steel were the rings made of, and how were they worked and treated? What kind of padding was used?

That seems really weird. It would be understandable if he'd been hitting an unpadded piece of mail against a log, or poor quality butted mail, but it's completely at odds with everything I know about how one-handed swords would be expected to fare against decent quality mail. You can see some testing of swords vs. replica armor here -- note that there are no serious penetrations with cutting or hacking attacks with swords, even though most mail in those tests is of poor quality, and some of it is even butted.

Here is a picture of substandard quality riveted mail after it was hit with a longsword over a piece of meat -- compare it with butted mail after it's been hit with blunted swords. There are plenty of test cutting videos, pictures and other reports available on the net, but I've yet to see a single one where decent quality riveted, padded mail over a target with some give (meat, punching bags, etc.) has been penetrated by a one-handed sword cut.

That I agree with. To get back to the original point, though, that's all just bashing the mail hard enough that some of the rings burst. Nowhere in these tests has anyone managed, or even really tried, to cut mail with a sword.

Maybe this is just showing that English isn't my native language, but to me applying a sudden force over a particular area isn't "cutting". If you replace a warhammer's spike with a narrow axe-head and smash an armor plate with that, to me that's not "cutting". When you cut a loaf of bread, you don't hack it with a knife like you're chopping wood with an axe. In my mind, if you say you "cut" something with a sword, that means applying pressure against the object and then drawing (or thrusting) the edge along the object to cut into it -- this can slice through unhardened leather armor, but it simply will not work with a sword against metal armor.

I realize this is just semantics now, but I would like to make it absolutely clear that cutting decent mail, scale or plate armor with a sword is just not going to happen. If we all agreed on that in the first place, then my apologies for going on about it.

Based on all the pictures and videos I've seen of swords vs mail testing, I have to disagree. In all those pictures, the individual rings are crushed and mangled, they do not exhibit any sign of having been sheared. In an extreme case, such as when a very sharp and very hard sword edge comes down on a small piece of mail stretched over something rigid, it could happen, but not in anything resembling a real combat situation.

I'd just like to point out that this is exactly what my magical mono-wire tends to be. Extreamly sharp (due to it's small size) and extreamly hard (due to it's high breaking strength).

Also, I've been running the numbers some more, and I have had to full embrace the concept of magical mono-wire. There is realy no way it can be as strong and as sharp as I would like it without being magic. Meh, reality is overated.