Armor changes things in sworsplay. If you've never trained in it, you can't imagine how it affects your movement and the execution of even simple actions. It has been said that while Europeans designed their armor to defeat swords, the Japanese designed their swords to defeat armor. There is a certain truth to this, but it's a simplistic view. The better Japanese armor was constructed of small overlapping lacquered metal scales or plates tied together with silk cords in order to specifically resist the slicing cut of the katana. It allowed significant freedom of movement while offering excellent protection. If it got wet, however, the silk cords soaked up water and it became terribly heavy. Although the earliest styles of samurai armor were designed with large square plates as a defense against arrows, the later forms were intended primarily to be used by and against similarly equipped swordsmen and to lessen the tremenedous cutting capacity of their blades. It was durable, effective, and provided for ample movement. How would it hold up the stabs of a narrowly pointed knightly sword? This is an important question.
Medieval European armor was designed and shaped more to deflect strikes and absorb blunt force blows from lances and swords. A knight's armor varied from simple byrnies of fine-riveted mail, which could absorb slices and prevent cuts, to well-padded soft jackets and metal coats-of-plates, which were designed to protect equally from concussion weapons as well as penetrating thrusts. A complete suit of fully articulated rigid plate armor required specialized weapons to effectively defeat it. Plate armor was constructed to be invulnerable to sword cuts- even, it can be surmised, those of the exceptionally sharp katana. Some high-ranking 16th century samurai lords actually owned pieces of contemporary European armor, gifts and purchases which they even wore into battle. They did not prize them merely as exotica. For foot combat, this armor was well balanced, maneuverable, and sometimes even made fo tempered steel. It was well surited for wear in combat, and is far from the awkaward, lumbering cliche presented in Hollywood.
Without weapons designed to defeat plate armor, any fighter armed with a swrod alone (katana or not) would have difficulty. Indeed, full European plate armor with mail might very well damage the keen edge on particularly fine katanas. After all, we should not forget that despite the katana's vaunted cutting ability, the samurai were able to successfully rely on their armors as defense against it. There is every reason to imagine knightly armor would have been just as effective if not more so. If we therefore assume the armors to be more evenly matched, say mail and partal plate for the knight as used around 1250, things would get more interesting. However, the samurai did often carry a thick dagger, which would have been quite useful against plate. Interestingly, each warrior was highly skilled in using armor-piercing daggers and with close-in grapppling (something not generally known about knightly fencing skills).
We must consider whether the knight in this hypothetical duel will be armed in the familiar shield and short sword style or will use only a single longsword? If armed with a shield, we must ask what kind? Will the knight employ a center-gripped type with front umbo or one worn by enarme straps? Will the shield be the highly effective "kite" shape with its superb defense or one of the smaller, more maneuverable convex "heater" styles? How about a thick steel buckler?
There's a reason virtually every culture developed the shield and why they were used for thousands of years: They were very effective. In 15th-century Europe, it was only the combination of the development of full plate armor and two-handed swords combined with heavy polearms and powerful missile weapons that finally reduced the long reigning value of the shield in warfare. The medieval style of sword and shield fighting is distinctly different from the two-hand grip and quick full-arm slashing cuts of Kenjutsu. Medieval short swords are properly wielded with more of a throw of the arm and a twist of the hips while making passing steps forward or back. Both cuts and thrusts were thrown from behind the shield while it simultaneously gurrads, feints, deflects, or presses. A sword and shield is a great asset over a single sword alone. Fighting wth sword and shield offers a well-rounded and strong defense that safely permits a wide range of both direct and combination attacks.
The shield was not used in the ways typically shown in movies, video games, stage-combat, or historical roleplaying organizations. Fighting against a medieval shield is not simply a matter of maneuvering around it or aiming blows elsewhere. A sword can cut quite well from almost all angles around or underneath a shield. Indeed, since the shield side is so well guarded, the opponent is the one limited to attacking to only one region- the unshielded side. As it comes out from behind the shield to strike, an attacker's weapon can be counter-timed and counter-cut, which is an effective tactic to employ against a shield user. Yet a shield user's attacks are not at all one sided. A shield can be used offensively in a number of ways and at very close range.
Katanas are powerful swords used with strong techniques, but thinking they could simply cleave through a stout medieval shield is absurd. A shield cannot simply be sliced through, even with a katana. Medieval shields were crafted of fairly thick wood covered in leather and usually trimmed in metal, making them highly maneuverable and difficult to cut into. More likely, a blade would be momentarily stuck if it struck too forcefully. Unlike what is seen in the movies or described in heroic literature, chopping into a shield's edge can temporarily cause the sword blade to wedge into the shield for just an instant and thereby be delayed in recovering or renewing an attack (and exposing the attacker's arms to a counter cut). Shields without metal rims were even favored for this reason.
Kenjutsu (Japanese swordsmanship), although consisting of very effective counter-cutting actions, also has no real indigenous provisions for fighting shields. A skilled warrior could certainly improvise some, but those unfamiliar with the formidable effectiveness and versatility of a sword and shield combination would have a hard time.
The Samurai's Sword
In major battles fought by both types of warrior, both samurai and kights typically wielded a sword in one or two hands. For the knight, the primary weapons had always been he long lancea nd the sword, and to a lesser degree, the poleaxe, dagger, and mace. The sword was always the foundational weapon of a knight's fencing training. For the samurai, however, the sword was but one of three major weapons, along wth the bow and the yari (thrusting spear) used from horseback. We should consider that, despite their later acquired reputation for swordsmanship, the samurai's primary weapon was, in fact, not the sword. The sword did not become a premier weapon of samurai culture and reach its cult status until the mid to late-17th century, when the civil warring period ended. It is something of a myth that every individual Japanese samurai was himself an expert swordsman (no more true than that every Wild West cowboy, such as they were, was an expert gunfighter). After all, the expression so associated wth bushido, at least in history, is "the way of the horse and bow", not the "the way of the sword". Besides, unlike knightly chivalric tales and combat accounts, the majority of single combats between samurai described in feudal Japanese literature took place with daggers and not swords. But for the sake of discussion, let us assume both fighters use swords in this imaginary case.
As a sword, the Japanese katana is unmatched in its sharpness and cutting power. Furthermore, it is particularly good at cutting against metal (but it only cuts through other swords in movies and video games). However, medieval plate armor is well known for its resistance to cutting, and cutting at a moving target hidden by a shield or a greatsword is not easy. While the edge of a katana is very strong, with a sharp cutting bevel, it is a thick wedge shape and still has to move aside material as it cuts. Although this is devastating on a draw slice against flesh and bone, it is much less affective against armors. Realizing this, several styles of Japanese swordsmanship devised specific techniques not to cut at armor, but to stab and thrust at the gaps and joinst of it just as the Europeans did against their own plate armor. Except for major conflicts in Korea and encounters against the Mongols, the katana developed in comparative isolation and is not quite the "ultimate sword" some of its ardent admirers occasionally build it up to be. The katana's exceptionally hard edge was prone to chipping, and needed frequent re-polishing, and its blade could break or bend the same as any other sword might. It was not designed to take a great deal of a buse, and is not flexible nor intended to directly oppose soft or hard armors as some forms of medieval swords had to be.
The katana's design was not set in stone. It was changed and altered over the centures like any other sword, being slowly improved or adapted to the different needs and tastes of its users in terms of cross section, curvature, and length. In the 13th century, for instance, its point had to be redesigned because it was prone to snapping against the metal reinforced "studded" leather armor (essentially equivalent to Europeans brigandine armor) of the Mongols and Chinese. By the 18th century its blade, no longer earnestly used against armors, tended to be made longer, lighter, and thinner for classroom practicing.
True, Japanese feudal warriors did have their own form of greatsword in the long no dachi blades. These, however, were employed specifically by lower ranking foot-soldiers against horses (and presumably, on occasion, against pikes). So we cannot draw an equivalency between these and medieval greatswords used in knightly fencing arts or to the true two-handers of 16th-century European battlefields.
Overall, the katana was a very well-rounded design: excellent at cutting and slicing, yet good at thrusting and suitable for armored or unarmored fighting on foot or horseback, either one or two-handed. It was a carefully crafted and beautiful weapon reflecting generations of artistry and fearsome necessity, but it was still only a sword- a man-made tool of well-tempered and expertly polished metal. Although the details of manufacture differed, they were made by the same fundamental scientific processes of heating and working ore by shaping and grinding as were other fine swords around the world throughout history.
The Knight's Sword
Having equipped our samurai, we must turn to the sword to be used by our knightly combatant. It must be understood that there was a great diverstiy of knightly swords and armor types. European swords were, in a sense, always specialized rather than generalized dsigns: There were swords for foot combat, swords for horseback, single and double-hadned swords, straight and curved swords, swords for armroed and unarmored fighting, swords for tournaments, swords for civilian dueling, swords ideal just for thrusting or just for cutting, and swords only for training.
A knight's sword was typically a one-handed weapon originally intended specifically for use with a shield. Their blades are wide and fairly thin, but rigid, with chisellike edges intentionally designed for cutting through mail armor and depp into flesh and bone wth a quick, forceful blow. They were light, agile, and stiff, yet flexible enough to withstand the tresses of use. They varied from the wider, flatter kinds to rigid, tapering, sharply pointed variations well suited for stabbing both plate and laminated armors. The later wide-based and acutely pointed style of bastard sword was superb for thrusting. So, even though Japanese armor was made of the same quality steel as their weapons, nothing in its crafting made it superior to armors European blades were designed to penetrate.
Although the medieval sword and shield combination was fairly common, longer blades usable in two hands were in widespread use from about 1250 to roughly 1600 in Europe. When we talk about medieval European longswords or war-swords (or even greatswords), we are not dealing with a single uniform style. Some swords had wide, flat blades with parallel edges well suited to powerful cuts. Later, swords specifically designed for facing heavier armor had narrower, much more rigid blades of diamond-shaped or hexagonal cross-sections that tapered to hard, sharp points. They were used to bash at armor before stabbing and thrusting into joints and gaps. They could also be employed to thrust like short spears or slam like warhammers, yet they were still capable of cutting at more lightly armored opponents.
The difference between these two European blades is significant and once more underscores the distinction between the manner of using a katana and a straight medieval Euriopean sword. The tapering blade form has a different center of balance and is often lighter. Its point of percussion is located farther down the blade, and its fine point is capable of making quick, accurate, and strong thrusts. The wider style can make a somewhat greater variety of strikes and delivers more effective cuts overall. The latter is more agile and easier to guard and parry with. It can also more easily employ its versatile hilt in binding, trapping, and striking. Its proper style of use (wth its tighter movements, various thrusts, and infighting with the hilt) is rarely depicted with any accuracy in movies and staged performances.
The reach factor also cannot be overlooked. Although a skilled fighter can effectively use a short blade against a long blade or vice versa, and although neither longswords nor katanas had standardized lengths, overall the katana is significantly shorter than European two-handed swords and greatswords. A longer weapon wth two edges does have advantages- especially if used by a man taller than the wielder of a shorter, single-edged weapon.
Surprisingly, the longsword or greatsword is arguably a more complex weapon than the katana. It has two edges that can be used, was well as a verstile crossguard and pommel permitting a variety of specialized techniques. Another element to consideris that European swords could be used in "half-sword" techniques where the second hand grips the blade itself to wield the weapon in bashing, deflecting, binding, and trapping as a pole-axe or short spear can be used. This was especially effective in fighting against plate armor.
Knightly blades could be excellent swords, but they are often denigrated merely as crude hunks of iron while samurai swords are venerated and exalted sometimes to the point of absurdity by collectors, enthusiasts, and films. The bottom line is that medieval swords were indeed well-made, light, agile fighting weapons equally capable of delivering dismembering cuts or cleaving deep into body cavities. They were far from the clumsy, heavy things they're often portrayed as in popular media and far, far more than a mere "club with edges". Interestingly, the weight of katanas compared to longswords is very close, with each on average being less than 4 pounds.
If instead of a sword and shield we match a knight with a longsword or greatsword against a katana-armed samurai, this makes a significant differenc in how we judge the fight. We must not fall into the trap of judging the medieval longsword in terms of what we know about classical Japanese fencing. It is a mistake to think that the straight, double-edged medieval sword with cruciform-hilt is handled like a curved katana. While there are certainly similarities and universal commonalities between the two styles of swordsmanship (such as in stances and cuts), there are also significant and fundamental differences. They each together make the same basic seven or eight cuts and thrusts. As a curved blade with an especially keen edge, the katana is superior in the potential use of quick, short slices. Yet, as a long straight blade tapering to a keen point, the longsword is better at thrusting. Additionally, its dual edges, enabled by a graspable pommel, allow it to attack along more lines than the eight standard cuts. Having two edges to work with permits back-edge and reverse cuts. This allows a larger number of strikes from different angles.
The katana is wielded in a quick, flowing manner with a torque of the grip as well as a push of the hips. Pulling a curved blade in this way makes it slice as it shears. The footwork is more linear, with short, quick hopping (even shuffling) steps. In contrast to the slicing slash of a curved, single-edged, Japanese blade, medieval swords were made for hacking, shearing cuts delivered primarily from the elbow and shoulder and employing wide passing steps. The movements are larger, with more fast whirling actions as the two edges are employed, the pommel alone gripped, or the hands changed to different positions on the hilt. As a straight blade, it strkes more with a point-of-percussion on the 6 or 8 inches of blade down from the point as opposed to the curved katana, which uses more of the first few inches. If we bring into the equation the medieval bastard sword with compound-hilt of side-rings and bar-guards as well as half-grip handle using various methods of holding, this could also be a significant factor. Such hilts allow for a variety of one or two-handed gripping options and gives superior tip control for thrusting or edge alignment.
When contrasting these two styles of sword we should also keep in mind a number of points. We classify each as longswords and both were designed for the same purpose: killing. Differences between them result from the particularities of their functions and the ways they accomplish the goals. We should also keep in mind that Japanese swords and sword-arts reflect a living tradition, and one with a long-standing interest group in the West promoting its study. In contrast, the medieval heritage has for decades had virtually nothing but Hollywood fantasy, medieval enthusiast groups such as the SFCA, and roleplayers representing it.
From this, it can be seen that a direct comparison of a European sword to a Japanese one is not possible. They are "apples and oranges", so to speak.
Onward to Conclusions...