Please note: I may not use the Japanese terms for everything in this document, or spell them the way you think they may be spelled. Deal. Different sources happen. Sources will appear at the end of this document. Oh, and I hereby give permission for AEG and any forum moderators acting as representatives thereof to post this (unmodified and in its entirety, except as directed by me) as a reference document anywhere they need to do so, if they feel so inclined.

SECTION ONE: INTRODUCTION AND ARMOR

Armor exists in a constant state of flux, always attempting to protect the wearer against an ever-more lethal variety of battlefield threats. There are many reasons NOT to wear armor. It’s expensive. It’s high-maintenance. It is hot and smelly (sometimes to the point of causing heatstroke). It restricts your mobility. It dulls your senses and slows your reflexes. It’s never perfect, 100% protection.

Therefore, it is reasonable to assume that if armor did not perform some valid battlefield function, people would not have worn it. People aren’t stupid. We may be more educated today, but people have a long history of seeing a problem, and then devoting all of their time and technological progress to that point in history finding a way to SOLVE that problem. Again, it stands to reason that, especially in a culture like that of Japan, where weaponry and armor simply did not evolve after reaching a certain level of technological development, there must be a rough balance between weaponry and protection. If armor was useless against battlefield weaponry, it would not have been worn. If armor was perfect protection against battlefield weaponry, weaponry would have evolved to defeat it.

When dealing with European weaponry, figuring out what weapons were used against what armors is a real problem. While there are some “through-lines” of armor and weaponry (like chainmaille and the humble spear –both of which were used nonstop and simultaneously for a good 1,500 years), armor and weaponry tended to evolve very quickly. Therefore, one could see all sorts of battlefield matchups. One could use a spear to skewer someone in leathers and a padded jack, and then immediately have to pull out a state-of-the-art flanged mace to deal with someone charging at them in cap a pie plate.

The Japanese aren’t like this. They hit a technological plateau roughly in the middle of the second millenium and, in general, stayed there. What this means for the historian is that his job just got a LOT easier. Again, in general, you can look at a 400-year period in history and understand that the basics or Japanese armor and weaponry just didn’t change to an appreciable degree. The cosmetics and details changed (look at the sode, or shoulder guards, of Japanese armor during the 1500’s and during the 1700’s and you’ll see what I mean), but the basic form of the armor stayed the same.

What does this mean for us?

It means that we can more readily look at simple examples. Performance of European armor can be significantly different when attacked by an Oakeshott Type XII sword or an Oakeshott Type XV sword that existed a mere 50-odd years later. We have the ability to look at a generic, representative suit of Japanese armor, and a generic, representative katana and say that they will have generally similar performance characteristics across a broad time span, specifically, that time span that impacts game design in L5R.

So, let’s choose a generic katana and set of armor then.

There are several types of armor we can look at. The O-yoroi, the do-maru, the haramaki, and a few others. Looking at these armors, however, reveals a general though-line. They are generally different layouts of the same basic protective materials. The materials in question are small steel lames (plates), 6 to 8 square inches in size, that are alternatively laced or riveted together or attached to various types of backings. Alternatively, there are armors that consist of a dozen or so large steel lames curved horizontally around the curve of the body, but the thickness of these plates is by and large the same as the smaller lames. While the layout changes, the basic protective materials remain the same. *

There are rumors of wooden, leather, or even reed/bamboo armors. Only leather (usually heavily lacquered) existed, and these are almost universally low quality “emergency” armors used for low-quality troops. It’s often better to have anything than nothing, and the psychological comfort these armors would have provided would help the soldier deal with the realities of warfare – though the protective qualities are certainly suspect. In any case, these armors are NOT the norm. They may be more common than indicated, due to their easier degradation over the passage of years – but they do not seem to appear in quantity anywhere in period documents or artwork. In short, with no primary sources for their widespread use, we must discount them from our study.

For our generic armor, we will choose an armor that closely matches armor seen commonly in card and rulebook artwork. This armor is the mogami-do. It consists of five horizontal plates laced vertically together, along with a kusazuri (half a dozen 3-5 lame plates laced around the bottom of the do to form a protective skirt across the lower hips and upper thighs). Kode (forearm guards – usually ¾” wide strips of steel laced to a backing of silk and 6-in-1 maille), sode (those cool squareish shoulder guards everyone loves so much), haidate (many-lame thigh guards) and suneate (lower leg and knee guards – usually cast in 3 vertically-aligned lames) can be added.

Mogami-do

Now because “Rokugan isn’t Japan” (glares at people who parrot this without thinking about where the source material came from), we’re going to use an L5R source for determining what constitutes light armor and what constitutes heavy armor. Reference pages 126-129 of the L5R: Roleplaying in the Emerald Empire rulebook (kudos, by the way, to the art and writing teams, for getting the terminology and pictures basically correct in this section).

Light armor consists of torso protection (the mogami-do) and upper thigh plates (the kusazuri). There are also watagami (shoulder straps) that are “grown” into shoulder plates, protecting only the top of the shoulders, similar to the upper left image above.

Heavy armor consists of torso protection (the mogami-do) and upper thigh plates (the kusazuri), in addition to upper and lower arm guards, upper and lower leg guards, and a helm of some sort (interestingly, the sode here includes, as it historically should, armor for the backs of the hands, called tekko, which appear only VERY rarely in the artwork, but were historically quite common; hand hits are a perfectly valid way to end a fight).

In short, light armor only covers the torso and hips, while heavy armor covers the whole body.

Three things determine protective quality in armor: deflection, hardness, and thickness. It takes more energy to penetrate thick protection; it’s harder to get a weapon to “bite” in something very hard (requiring yet more energy to penetrate the armor), and deflection essentially reduces the amount of energy from an attack that can focus on penetrating the armor.

Steel Japanese armor tended to three thicknesses. Small lames were roughly analogous to 18-gauge steel, and larger lames were about 16 gauge. Thicker 14 gauge was used for single-piece globular breastplates, but these lay outside the realm of this discussion.

Japanese armor tended to have very poor deflective qualities. The armor is somewhat contoured to the body, meaning fewer acute angles to deflect blows. Additionally, the armor tends to be covered with lacing and/or divided into small plates. Both of these produce a tendency of an incoming blow to “stick” to the armor – it gets caught in the surface elevation gradations and will transfer more energy to the target, rather than sliding off to the side and wasting energy on the air. The most blatant examples of this are large, ornate kabutos with big shiny symbols on the front. A direct downward blow into these should result in the blow sliding off the side of the helm, but instead the symbol traps the sword against the helm and redirects the energy back into the blow. (Yes, I’m aware these were often made of soft metal or were on “break-away” mounts. Neither always works…).

Japanese armor tended to have reasonable hardness. While some variation is expected, steel is a hard substance, and thus resists impulse against it. This high surface tension resists slicing actions along its surface, failing only when directly impacted by more energy than the surface tension can withstand – crumpling and (if crumpled too far) tearing under the impact. Remember this. This’ll be important later. This thing to remember is you cannot SLICE through steel under normal conditions (like with what someone may be carrying on a medieval battlefield). You can crumple steel, and you can cause it to tear with a very strong cut (which is mechanically different than a slice), but you cannot simply slice through it like you would a block of cheese.

Armor has two additional properties of note: weight and restrictiveness.

Japanese armor is fairly light for it’s surface area. It’s made of thinnish steel, and with significantly less coverage than European cap a pie plate. A comparison: jousting plate is head to toe, 16 Ga. on the arms, 14 Ga. on the legs, back and helm, and 12 Ga. on the torso and left side of the helm (differential helm thicknesses are common historical occurrences, as most lance impacts came from the left side). The only gaps are directly in the armpits, backs of the knees, backs of the hips, and in the palms of the hands (I don’t count oculars in this, since every armor has them). Plate like what you see below weights 52 pounds, distributed over the entire surface area of the body. Heavy, right?

Wrong.

European Cap a Pie plate from Historic Enterprises, ltd.

The common US infantryman carries a 60-pound rucksack, 3 lbs. of rifle ammunition, 5lbs or more of water, a 9-lb weapon, 3-4-lbs of grenades, a combat knife, stuff in his pockets, and more. It’s not uncommon for the soldier to go into a firefight carrying 90 or more pounds of stuff, and still have to fight and be agile enough to avoid fire. Heck, 60 pounds of it (more than that entire suit) is just on his back. The soldier learns to fight, over 12 weeks of BCT and another 3-6 months of AIT, to fight with this load on him, and nobody has doubts about his ability to do so. Now imagine someone trained to fight in that load for two years, five years, or even more, except the load is evenly distributed, and custom-made to fit him. The weight of European plate isn’t a problem. The weight of Japanese armor is even less so. It’s made of thinner materials, lighter materials, and doesn’t protect as much of the body (the arms, especially, don’t get a whole lot of protection). Weights of Japanese armors vary, by it's usually in the region of 40 lbs. for what L5R would consider "heavy Armor" The mogami-do depicted above weigh 17 lbs. and 19 lbs., respectively, and by themselves constitute Light Armor.

Restrictivness is the last armor quality, and here the Japanese have a great advantage. Don’t get me wrong, European armor isn’t as bad as Hollywood makes it out to be. While in plate, I can reach over my head and touch the opposite ear, for example, or touch my opposite shoulder, or even do the splits (well, before having my groin ripped in a tragic ice hockey incident too horrible to describe), but there IS a loss of mobility. Wearing yoroi, though…man it’s nice. Because so much of it is laced, certain points may be left loose or stretch so that there’s practically no mobility loss at all. The kusazuri allows for full hip movement, the solid knee cop on the suneate never jams or blows a rivet (resulting in a stiff-legged gait), and the arms…wow. The upper arms are protected by silk and chainmaille, two highly supple fabrics. The Sode are often strapped down to the triceps, but are thin enough that they don’t impede arm rotation in pretty much any direction, and the wrist mobility is incredible – again, because the wrists are lightly protected.

Looking at Rokugani armor, light armor shouldn’t impede mobility in the slightest, except possibly bending at the waist (the Japanese never did to well with articulated sliding rivets), but depending on the armor style even this isn’t a problem. There simply isn’t enough there to get in the way. Heavy armor has an issue with the shikoro (the skirt around the bowl of the helmet) – it impedes your ability to strike from above. Kenjutsu got around this with the hasso no kame stance. At a risk of making the wrong impression, look at Qui-Gonn Jinn in Star Wars. He habitually adopts a hasso no kame stance with his lightsabre (though he holds his elbow WAY too high!). For a further Star Wars reference, watch how Darth Vader makes overhead strikes with his weapon. The blow is never vertical from above the head. It’s always diagonal from around the area of the upper shoulder. And look! He has a helmet shaped very much like a Japanese helm…

In short, Japanese armor was mediocre (but not BAD!) on thickness and protective value, but long on flexibility and ease of repair.

So, that’s finished our discussion of the properties of armor. Next, let’s talk about swords and how to use them. After that, we’ll get into how the twain would interact on the battlefield.

*There are armors that consist of single pieces – globular or peascod breastplates. However, these universally postdate the appearance of European traders into Japan. As Rokugan has categorically rejected ANY gaijin influence (as opposed to Japan, where gaijin innovations were accepted “on the sly”, as it were) I chose to ignore these armors in the study. They would not fit in Rokugan for this reason, and indeed do not seem to appear in the artwork (or, if they do and I’ve missed it, they appear in such a small percentage of armors as to be statistically insignificant).

SECTION TWO: THE SWORD

The katana is the outgrowth of the tachi, a slightly longer sword on different mountings. The katana is notable for being described in several sources as the medieval world’s most perfect slicing weapon. That is an important and insightful distinction, and one we will cover in greater depth. But first, a bit of history.

Early in the Muromachi period (circa 1336-1573) there was a large change in tactics from relatively large numbers of horse to large numbers of foot troops. As such, the katana evolved from the tachi. The early katana were shortened tachi and have the heavily curved shape of earlier Kamakura blades. As the years went by, the weapon mutated into the classic Muromachi katana, a blade between 27-30 inches in length with moderate sakisori (blade curvature), little funbari (lengthwise blade taper) and chu-kissaki (a short tip). This set the pattern of the katana for basically the next 500 years.

Muromachi katana

Additionally, these were the blades that would have seen the most use in the Warring States Period of Japan, the Sengoku-Jidai. They are important in that they have the most curvature, as a “class” of swords, seen in Japan from this period to the end of the widespread use of swords as a combat weapon. In Rokugan, these swords don’t seem to appear very often, as their curvature makes them very distinctive when viewed from most angles.

The most common swords we see in our game (and the most common katana in collections today) are of the Shinto style found during the 250-year peace of the Edo period. While there were some variations in shape within the Shinto period, the classic style is that of the Kanbun era (mid 1600's). Blades are made in katana length, circa 26- 29 inches, but stouter and with very little curvature (approximately 1cm) and chu-kissaki. Kanbun style blades are nearly straight and quite robust. Looking at the portraits on and above my computer by April Lee and Steve Argyle, the idea that the most common blade in Rokugan is of this style is borne out.

Katana of the early Edo Period - note the lack of blade curvature compared to the Muromachi

As many good things do, the era of combat blademaking started drawing to a close late in the Edo period. One starts seeing “show” swords, with wildly exaggerated hamon (temper lines) and large amounts of guilding and jeweling. This is analogous to the large, 20-lb. parade swords seen during the late European Renaissance – the sword was falling out of service there as well, but people still wanted to carry them to look good (it is from these examples, never exposed to combat and thus in good condition and therefore in museum display cases, that the idea of 20 and 30 pound swords was introduced). There was an attempt at a swordmaking revival around 1780, and this revival marks the Shinshinto sword period. Suishinshi Masahide is generally credited with leading a rival of sword making, promoting a return to the styles and methods of the Kamakura period (around 1100), which meant a bunch of katanas that were essentially shortened tachis became popular.

Katana of the Late Edo Period - much more curvature

Because the number of Shinto style katanas found in Rokugani artwork, we will concentrate solely of them for our studies about how the weapon interacts with armor. This is not a bad thing, as it was the last style of katana to see constant, consistent use against armored battlefield foes. Earlier styles don’t appear often enough, and later versions performed more often against unarmored “civilian” opponents (in duels and the like). As it’s also the most common style of katana extant and reproduced today, there will be more data available.

So how is a katana used?

Well, there’s a glib answer: you cut stuff with it. However, a more specific answer is probably necessary, so we’re going to have to take a short side trip into combat theory.

The goal of any fighter is to render his opponent incapable of fighting. Most often, this means killing him as quickly and efficiently as possible, but it can also include rendering him incapable of mounting offense or defense against you (often followed by killing him). There are only a limited number of targets on the body that allow one to do this. A blow to the head is obvious. It will result in death with only a little penetration (about an inch on the top of the skull), and even if it doesn’t kill, it’ll rattle your opponent around badly enough that it will be difficult for him to mount a defense against the follow-up attack you make. Hitting an opponent here is preferred, because there usually isn’t a period in which he’s mortally wounded but still dangerous. He just drops.

Killing your enemy is also done quickly and efficiently with a thrust to the vertical centerline of the upper chest, throat, and face area (above the nipple line so you’ve got the best chance of avoiding the rib cage). You’ll sever windpipes, aortas, jugulars, carteroids…all sorts of important people bits. Death or incapacitation from a wound in this area takes a few seconds, but it usually pretty quick as long as you’re on the centerline. Thrusting to the sides of the centerline will also usually result in death, but it can take a LOT longer – you’ll usually get a lung, which can take a while to drown the victim, or to lose enough blood to pass out.

Finally, the third best area in which to incapacitate an opponent is anywhere in the body cavity where you can do massive damage – the more the better as it increases the chances of the enemy going into shock and dropping right away. Naturally, if you can avoid bone, you’ll get more tissue damage, so horizontal strikes to the abdomen are the blow of choice here. Even a shallow cut (about 2 inches deep) can disembowel an opponent, and this is the place where you have the best chance of bisecting him completely, as (if you’re on target) the only bone to sever is the spine itself.

There are also some target zones to incapacitate the opponent so you can make the killing strike in safety. The most obvious and most overlooked ones are the hands and wrists. If you can’t hold a weapon, you can’t fight, and those hands are pretty fragile assemblies. What’s more, they need to be mobile to fight, and that means you can’t armor them heavily. Why you want to target them over the arms as a whole is that, by definition, the hands and wrists are exposed when your opponent makes a strike. They will always be the closest part of your opponent to you, which means you have to extend yourself the least to strike them. Unfortunately, many systems of fighting today forbid the intentional targeting of the hands and/or wrists, which is why this target gets overlooked a lot.

The other good targets are the collarbones. Anyone who’s ever broken one (*raises hand*) knows that you can’t lift your arm more than a few degrees with a broken collarbone. They’re fairly thin bones, as long bones go, and they're nice and level, which means that a downward blow to the shoulder will hit them perpendicular to their direction of strength, with a high probability of a break. The topper is that you can’t armor your collarbones heavily at all, because the whole area compresses when you lift that arm, and there’s no way to easily generate a deflecting surface in that area without restricting mobility more than the armor user will want. Very large sode can help, but more often than not it’s just an area you can’t protect well.

Now you’ll note that the legs aren’t on here at all. You don’t want to attack the legs. By definition a strike against the legs moves your weapon out of the “blocking box” around your torso and head that keeps you alive, and even worse, a strike against the legs is no guarantee of a kill – the really important arteries in the legs are tough to hit with a cutting weapon, and the knees and ankles are simply too low to be good targets. It’s one thing if you’ve got a shield (or you have to cut around one), but with kenjutsu, your katana is both your sword AND your shield. You need to keep it between you and the other guy.

Now that we know where to hit, we come up on how to hit…

The primary destructive action of a katana is a slicing one. This is an important bit of semantics, as there is a distinct difference between the mechanics of a sword cut, and a sword slice. To confuse things more, I will be using the term “cut” as a verb to denote ANY attack with the blade of the sword, and will then clarify whether the specific destructive motion is a cut or a slice.

There are two mechanics to every sword cut. There is impact. Impact is the amount of force or impetus transferred by a collision of two objects. It can be measured in several ways, in foot-pounds, or joules of energy released, and so on, and is a function of both the speed of the weapon strike and the mass behind the weapon. Increasing either speed or mass will increase impact – unfortunately the speed of weapon strikes is relatively immutable. A person can only swing a weapon so fast, though increasing length (and thus tip speed) can help. The easiest way to increase impact is to increase mass at the tip (hammers, axes, et al.). Weapons such as a hammer depend almost entirely on impact. When a weapon strikes a body, the impact transfers the unused kinetic energy of the attack to the target’s body, where is it then dissipated throughout the surface area of the strike zone. A small strike zone surface area (the area actually struck by the weapon) makes it more difficult to dissipate the impact, and can therefore do more damage to a target (i.e. why I‘d rather get hit with a 10-lb body pillow than a 10-lb sledghammer).

The second mechanic in a sword cut is cleaving action. This is a simple mechanic in theory. It interposes a sharp edge of a weapon between molecules of a target and forces them apart. The stronger the bonds between molecules, and the denser the molecules are packed, the harder it will be to get the weapon edge between them and to separate them. The thicker the substance, the harder it will be to force the edge between ALL of the molecules comprising the thickness of the substance. So the two things that resist cleaving action will be object hardness and object thickness.

Different swords work in different ways, but all swords include both mechanics. Any time a weapon is swung into a target there will be a transfer of energy, necessitating impact. Swords, by definition, are edged weapons. Therefore, they will force apart molecules and perform a cleaving action. The Holy Grail of swordsmiths is to have a weapon that maximizes both mechanics and is still light enough to use. Some swords work more on the impact side of things (falchions), and some work more on the cleaving side of things (tulwar, katana), and try to strike a balance (many arming swords).

A sword “cut” (as opposed to a slice) goes for impact over cleaving action. The amount of cleaving action is not inconsiderable; molecules are separated by a sharp edge impacting them at high velocity.

A sword slice goes for cleaving action over impact. While cleaving action can be achieved through impact, the lion’s share of the damage in a slice is done from a sharp edge being pulled under pressure through and between the molecules of a substance.

For the katana, we look at the slice. When swinging a katana at a target, the goal is to have the blade of the sword impact the target around 6 to 8 inches from the end of the blade (the sword also being a lever this increases impact; a sword’s cutting arc being a circle the end of the sword will be moving very fast compared to the center of the arc [the hands]) and opens an initial wound. Immediately upon impact, the bottom hand on the hilt pulls toward the body slightly. This pulls the end of the sword back towards the wielder, dragging the last 6-8 inches of the blade (and its attendant sharp edge) through the opening made by the impact, slicing open even more soft, yielding flesh. Blade alignment and sharpness are critical to this (oppositional twisting of the hands on the hilt during the strike preserves blade alignment) cleaving action. If the sword edge isn’t vertically aligned to the depth of the cut, energy and cutting power are wasted. If the edge isn’t sharp, it takes more power to drag the sword through and separate those pesky molecules, thus wasting energy that could be used to do yet more damage to the target.

Fortunately, the Japanese made very sharp swords. The hardness of the edge allows them to hold that edge for longer, thus lessening the chance of energy being wasted in a cut from a dulled edge.

Let us be clear: while the impact of a katana upon a target can do significant damage, it is the slicing motion of the blade that inflicts the most grievous harm. The katana is made as a slicing weapon: to use it as such is to use the weapon to maximize its destructive capabilities.

SECTION THREE: ARMOR vs. SWORD Now that we’ve established type type of armor we’re discussing, and the attendant representative sword with which we will compare against it, let me make a controversial statement.

A sword, under battlefield conditions, cannot reliably defeat armor of the typical thickness worn by samurai.

There. My “bias” (as some will call it) is out in the open. Let me support it.

We have established that the typical thickness of steel worn by the samurai is measured as being between 16 and 18 gauge. This means that the armor cannot be appreciably thinner than 1.1938mm thick, and cannot be appreciably more than 1.524mm thick.

It requires, (not “is recommended”, but requires) approximately 55 Joules of energy to achieve 45mm of penetration of 1mm of steel from an arrow striking perpendicular to the steel. Why an arrow? The numbers are more easily available. That, and if we figure the numbers for the arrow, it actually weights the test towards the sword. And arrow has a far lower impact area than a sword blade, so if armor can protect against an arrow, it can definitely protect against a sword.

In any case, it takes 55J of energy to penetrate 1mm of steel. It takes 110J to penetrate 1.5mm, and 175J to penetrate 2mm. Looking at the armor thicknesses for a mogami-do, it should take something between 60J and 115J to achieve 45mm of penetration. 45mm is about 2 inches, which is generally considered to be the minimum penetration needed to kill an opponent, or to cause a debilitating and fatal wound.

Judging from tameshigiri practitioners (the guys who cut the tatami mats), katana are swung in the vicinity of 45-50 mph at the center of percussion (the spot on the sword where you want to hit). Simple physics dictates that a swordlike object moving at some 48mph is going to generate something like 50-55J of energy. In short, you’ll probably get through very thin metal, you may break open slightly thicker metal, but you’re not going to get good penetration against any thickness of armor commonly seen on the Japanese battlefield.

In addition, the energy required to defeat a mogami-do isn’t just based on beating the plates. Mogami-do are laced together. When a single plate is struck (or a few plates in a small area are struck), the rest of the plates surrounding the impact area will give slightly, further absorbing energy. The lacing will stretch and give slightly, further absorbing energy. Each plate is curved away from the body – a surface curved vertically is more difficult to penetrate horizontally (an I-beam works on the same principle, as does a fuller on an arming sword – it stiffens the structure). Which means yet more energy is required to defeat the metal. Finally, the deeper the cut, the more metal has to be moved aside. Essentially, resistance increases as you penetrate deeper.

Further, if all the math doesn’t get you, let’s look at some real world examples.

In Japan, there is an activity called kabutowari, or “helmet-splitting”. It’s where they take a katana, and take a real live period kabuto, and try to cut through it. This has been going on for centuries, as it’s a better test for how a katana performs than the more famous “cut 5 criminals in half” test. (Unless, I suppose, you dressed the criminals in the armor, but I’ve yet to find any source that says the Japanese ever figured that out.) The test is performed by setting up a kabuto, taking a sword of your choice, and hitting the kabuto as hard as you possibly can, and then measuring the length of the cut.

From my research, I’ve been able to find several examples where the katana “performed adequately” or “as expected”, but never any detail on exactly what happened. The sole places I’ve found specific measurements are all post-Meiji Restoration kabutowari. However, I would point out that as they are all using actual historical examples for both weapons and armor, they serve as valid tests for our purposes.

The world-record cut (the longest ever achieved while the lengths were being recorded) happened in 1994, against a Hineno style kabuto dating from between 1573-1602. The world-record kabuto cut with a katana is 13.08cm (approximately 5”) in length. Other, earlier cuts are 10.58 cm (1886) and 12cm exactly (1986). It is worth noting that during the 1886 cut, it took three swordsmen to get to that length. The first man’s sword rebounded from the helm, and the second man’s did as well, actually causing him to fall.

So, we know that a sword cut to the helm during a kabutowari measures about 4-5 inches in length, but how deep was it? The length of a cut doesn’t matter so much, as it is cut depth that determines damage to a person. Again, math.

The bowl (the section covering the top of the head – and the target for most attacks) on any given helm can basically be described as a hollow semi-sphere X” in diameter. The smaller the diameter, the greater depth a given cut length will have against it. Most helms have a bowl of 10-12” in diameter, allowing room for suspension and padding. Assume a bowl of 10”, to give maximum possible penetrative power to the sword (and weighting the test against the armor). A straight 5” line drawn across a circle of this diameter produces a depth of about ½”. The curvature of a katana may add a little more than a single centimeter (for a VERY curvy Shinto katana) in depth, for a total penetration depth of perhaps an inch.

Diagram showing a 5-inch long straight-line penetration of a 10-inch diameter circle. IMAGE NOT TO SCALE

Is an inch of penetration enough to kill a man? From a blow to the head, possibly. However, it’s also worth taking a look at the conditions of this test. The target is a stationary one, just above waist level, giving the wielder the assistance of time and gravity to bring his arms all the way through the cutting motion, and to build up maximum velocity. The target isn’t fighting back. The wielder also has time to get himself set for the attack. He can perform breath control, stabilize his body, brace himself for the impact, and set up the most perfect torque in his strike. It’s literally cutting in perfect conditions.

With all that, the world-record cut is getting about an inch of penetration.

Some applicable images from the 1994 World-record Kabutowari:

The wind-up. Nobody would ever do this on a battlefield. It’s suicide.

The strike. Note the spray of metal shards from the helm. Also note how far the sword has rebounded from the helm itself

The aftermath.

The aftermath showing the depth of the cut. Note that it’s about an inch deep, as previously noted. The sword would be embedded in the skull of the target, but probably not into the brain. This is a disabling wound, probably fatal, but look how vulnerable the swordsman had to make himself to get it.

There is an interesting conclusion to be drawn from this. You’ll note that the practitioner depicted here is NOT cutting correctly, as we’ve defined a correct “slice” with a katana. He’s winding up and slamming the weapon as hard as he can into the helm. This is odd, and tells us that a slice is not the correct way to attack armor. After all, if it was, wouldn’t the guy who set a world-record be doing it? Unfortunately, we’ve seen that a slice is the correct way to employ the katana that takes advantage of the weapon’s strengths (sharp edge, curved, etc.).

So what killed all those samurai? If a sword blow isn’t going to kill someone in armor flat out, what good does it do to hit someone?

Here’s the thing. Just cause a blow didn’t penetrate or severely wound someone doesn’t mean it doesn’t hurt. As is obvious, a blow to the head will result in the target being dazed, leaving him open for followups to unarmored areas, and we won’t be able to defend against them because he’s dazed. Secondly, a blow to armor may not penetrate, but it can damage the armor. I can speak to this. I’ve had rivets blown from weapon impacts, which cause leather strapping to break or give way, and all of a sudden I’ve got an 8-lb. hunk of metal hanging off my body in a funky way, throwing me off balance and getting in my way. In a way, Japanese armor is better, because it’s really hard to flat-out break silk. In a way it’s worse, because a cutting, slicing weapon (like, say, a katana) can slice said lacing, leading to the same problem.

Finally, I would hypothesize from my own experience that the larger number of battlefield deaths from katana were due to thrusting attacks, not to cuts. First, thrusts are dangerous. About 2 inches of penetration are needed to reach vital organs, while a cut can slice through many inches of muscle or even bones without killing.

Secondly, it is easier to target a thrust that will bypass armor than a thrust. Once a target is stunned or injured, the tip of the weapon can almost be placed on its target, and simply shoved home.

Third, the mempo (face guard) on a kabuto is massively uncomfortable to wear, and protects against any form of impact very poorly, as it lies flush against the skin. It wouldn’t be worn if it wasn’t useful, therefore thrusts to the face must have been common. I also point out that that several historical documents point to samurai removing their mempo for better visibility and ventilation (European knights were prone to doing this with visored helms as well). That creates an obvious vulnerable point in the samurai’s armor. Here my sources fail me – I can’t find Japanese sources saying that facial injuries were common. However, I believe they must have been. When knights did the same thing, it is often mentioned that someone was killed via a thrust or arrow to the face, though they were otherwise uninjured. In some sources, it seems to be the only source of injury. If it happened so often to armor-clad knights, it probably happened with similar frequency to similarly un-face-protected samurai.

Finally, all battlefield swordplay includes a large number of throws. Interestingly, most of these throws end with the tori bending at the waist over the thrown uki. Also interestingly, I can’t help but note that when I perform the throws, more often than not my sword shoulder is lined up perfectly with my opponent’s face. From that, it’s a short step to simply straighten my arm from the shoulder and drive the sword in that hand directly into my opponent’s face, or at least his upper chest.

We can get another clue about how to defeat armor from a refinement to that swordplay. Modern Kendo includes only 8 targets. There are the three men (head) blows, straight down, and diagonally to the right and left. There are the two do (body) blows, horizontally to the right and left. There are two kote (wrist) strikes, one two each wrist. Finally there is the tsuke (throat) thrust, aiming roughly at the notch where the collarbones come together at the front of the throat. All of these are immediately- disabling strikes against a person out of armor, and almost all are disabling against someone IN armor.

The vertical men strike is the one depicted against the kabuto above. It’s utility is obvious.

The two diagonal men strikes are lethal against an unarmored opponent, and can easily be retargeted against the light-armored collarbones against an opponent wearing armor.

The two do strikes are about the only way to get a perpendicular strike (thus maximizing power and minimizing deflection) against someone’s torso in armor. Of course, they’ll readily disembowel someone not in armor.

The wrist strikes incapacitate an opponent, either to end the fight or as a setup to a lethal followup. As noted, the wrists cannot be heavily armored, due to mobility constraints, and thus remain a valid target whether the opponent is armored or not. And, again, whenever an opponent strikes at YOU, his wrists are exposed by default.

Finally, the tsuki thrust can hit the throat, upper chest, or even the face – whatever is convenient or looks unarmored. Any of these means death.

Each of these targets is small and easily defended, thus the goal of the armor is to deflect blows to the wearer, absorb what cannot be deflected, and to convince the opponent to try to hit a small, mobile target that will leave the enemy exposed when he tries to strike.

To reiterate: armor is effective. First, there are social reasons. If it wasn’t effective at what is did, it would not have been worn; the benefits had to outweighed the considerable drawbacks. Since armor WAS worn, it had to have protected well. Secondly, the math proves you can’t simply cut through armor. A world-record-setting human can…barely…generate enough strength to provide half as much penetration as is needed to kill the target, while using a striking technique that intentionally does not employ the weapon to the fullest. Third, the effectiveness of armor is proved by a martial system that has created techniques devised to bypass armor and attack lightly-protected or unprotected spots, as well as the appropriate counters.

SOURCES: http://www.sengokudaimyo.com/katchu/katchu.html http://en.wikipedia.org/wiki/Sheet_metal_gauges http://swordforum.com/ http://www.shinkendo.com/index.html http://www.thearma.org/essays/parry.htm http://www.thearma.org/essays/knightvs.htm http://www.thearma.org/photos/Gathering ... utting.htm

______. Nihon katchû ronshû (Collected discourses on Japanese armour). Tsukubane Co., Tôkyô. 1991.

Arai Hakuseki. The Armour Book in Honchô Gunkikô. Trans. by Y. Ôtsuka. Ed. by H. Russell Robinson. The Holland Press. 1964.

Bottomley, Ian. Japanese Armor: The Galeno Collection. Berkeley, CA. Stone Bridge Press, 1998.

Mathews, David (AKA Sven Vandeleven, KSCA, OL). "Japanese Retainer Armour 1550," The Hammer. Reprinted in The Best of The Hammer, vol. 2. Ed. Brian Flax. Raymond's Quiet Press, Albuquerque, NM. 1985.

Sakakibara Kôzan. The Manufacture of Armour and Helmets in Sixteenth Century Japan. Trans. by T. Wakameda. Revised by A.J. Koop and Hogitarô Inada (1912). Revised and edited by H. Russell Robinson (1962). The Holland Press, Ltd. London. © 1962. Second edition, 1979.

Shimabakuro, Masayuki. Flashing Steel: Mastering Eishin-Ryû Swordsmanship. Frog, Ltd. Berkley, CA. 1995.

Suno, Nicklaus. Practice Drills for Japanese Swordsmanship. Weatherhill Books. New York, NY. 1996

Tobler, Christian. Fighting with the German Longsword. Chivalry Bookshelf, Highland Village, TX. 2004.

Tolhoffer, Hans. Medieval Combat: a 15th Century Illustrated Manual of Swordfighting and Close-Quarter Combat. Trans. By Mark Rector. Greenhill Books, London. 2000.

Yamagishi Motoo. Nihon katchû no jisshôteki kenkyû (An empirical study of Japanese armour). Tsukubane Co., Tôkyô. 1997.

ABOUT THE AUTHOR: [REDACTED].

MECHANICAL CONCLUSIONS

Armor is simply better than the game mechanics give it credit for. Ergot, the following changes are recommended (and if AEG feels like using them, you've sure as heck got MY permission! )

I assume the following: 1) Offensive and defense techniques used to bypass armor or defend against it generally cancel each other out.

2) The average human’s strength is entirely used up in penetrating a single piece of metal equivalent to that used in a period kabuto. The average human has a Strength of 2.

3) I’m trying to rewrite as little as possible of the rules.

Mechanics: -If not directly changed by this section, a given rule regarding armor remains the same as in the RAW

-Armor drops unkept dice off of weapon damage (to a minimum of 0). Ashigaru and Light armor both drop 2 dice (equal to the strength of an average human!), Heavy and Riding Armor both drop 3 (due to overlapping plating and addition of maille). This mechanic is termed the “absorbtion rating” (AR). This AR is not modified by any school. – so Crab don’t get bonuses to the thickness of their armor, they just learn how to use it (improve deflection angles and thus gain TNtbH modifiers) better.

-TNtbH mods stay as-is, due to the difficulty of getting a solid, damaging strike in amid the deflection surfaces. This is a “deflection bonus”. The deflection bonus has no effect against someone trying to initiate a grapple.

-This damage is dropped BEFORE conversion of unkept dice into kept dice. -Weapons that grant Strength bonuses keep this bonus, representing their superior armor-defeating properties.

-Weapons that ignore armor TNtbH modifiers still do so, as deflection is a separate defense than absorption. This has no effect on AR.

-In addition, called shots have a reason to exist. Ashigaru armor covers only the torso. Light Armor only covers the torso and either the arms (and hands!) or legs (player’s choice). Heavy Armor and Riding Armor both cover all limbs, the torso, and the head. Raises to bypass armor will ignore AR. EDIT for clarity: The original TNtbH bonus of the armor still applies to this called shot - to be keeping with the RAW.

-Armor provides no AR in a grapple if an opponent is using a weapon of tanto/aiguchi size.

-Armor AR has no effect against "raw" magical damage, but do apply against the "elemental weapon" spells, such as Yari of Air.

-Light and Ashigaru armor incur no penalties to their use.

-Heavy Armor incurs a +5 penalty to Athletics TNs and a –5 penalty to attempts to win control of a grapple.

-Riding Armor incurs a +10 penalty to Athletics TNs, a –5 penalty to attempts to win control of a grapple, and reduces the wearer’s Water Ring by 1 for purposes of movement only (while off the horse only, obviously).

-Blowguns must make a called shot to hit an unarmored portion of the body.

-Armor qualities may have the effect of ignoring penalties for wearing armor or adding slightly to the deflection bonus at the GM’s discretion. Under no circumstances should any armor of less than legendary quality have even the slightest chance of adding to AR. A Clan Champion’s Heavy Armor might have an AR of 4 instead of 3.

This playtest redefines what armor-piercing arrows do as well. “After” modifiers replace “before” modifiers Before (as per RAW): Willow leaf: 2k2 AP arrow: 1k2 (ignores TN bonus) Flesh-cutter: 2k3 (doubles TNtbH bonus)

After Willow leaf: 2k2 AP Arrow: 1k2 (subtracts 2 from the AR of the armor to a minimum of 0) Flesh Cutter: 2k3 (adds 1 to the AR of the armor)

Examples: Samurai with Strength 2 and a katana attacks a Samurai in Light Armor Katana with Str 2 vs light armor=5k2-2k0=3k2 damage total

Samurai with Strength 2 and a katana attacks a Samurai in Heavy Armor Katana with Str 2 vs Heavy armor=5k2-3k0=2k2 damage total

Samurai with Strength 4 and a katana attacks a Samurai in Light Armor. Katana with str 4 vs light armor=7k2-2k0=5k2 damage total

Samurai with Strength 4 and a No-Dachi attacks a Samurai in Light Armor. No-dachi (add 50% str) with str 4 vs light armor=9k2-2k0=7k2

Samurai with Strength 2 and a tanto attacks a Samurai in Light Armor. Tanto with str 2 vs light armor=2k1-2k0=0k0 (no effect)

Samurai with Strength 3 and a Yumi fires an AP arrow at a Samurai in Heavy Armor. 1k2 (arrow)+3k0 (bow)=4k2-0k0=4k2.

Samurai with Strength 3 and a Yumi fires a Willow Leaf arrow at a Samurai in Heavy Armor. 2k2 (arrow)+3k0 (bow)=5k2-3k0=2k2

Samurai with Strength 3 and a Yumi fires a Flesh-cutter arrow at a Samurai in Heavy Armor. 2k3 (arrow)+3k0 (bow)=5k3-5k0=0k0 (no effect - and you shouldn't be using a flesh- cutter against someone in armor anyway)

Conclusions Yes, this means than an average strength 2 samurai with a 0k1 weapon does nothing to someone in armor. That’s why armor exists. Want to deal with the guy in armor? Get a bigger weapon and/or magic. Or go after him out of his armor. Or grapple him. Armor provides an advantage – that’s why it exists. It also means average people can have a real problem with a target in Heavy Armor, but this is counterbalanced by the fact that relatively few Samurai get routine access to Heavy Armor, and there’s several ways to get around it (grappling especially). And you can always make Raises for extra damage as normal, which seems to be where a lot of damage comes from anymore.

The sole problem with this is that monks kinda get screwed. I would rule that monks get Ref x (5+[School Rank/2 rounded down]) as their TNtbH, which becomes the normal Ref x 5 if they are wearing armor for any reason.