Katana... In Depth.
This is not a rant.
You may notice it is not the katana itself I dislike, but the level of hype surrounding it.
Most of my research deals with comparitive studies, comparing the katana against Western swords. Two good articles on the subject are ARMA with Katana vs Rapier (
http://www.thearma.org/essays/katanavs.htm) & Knight vs Samurai (
http://www.thearma.org/essays/knightvs.htm).
A katana blade is effectively made of two different types of metal - an extremely hardened tempered cutting edge to achieve that legendary sharpness, and a thick wedge shape of far softer iron to reduce the shock and vibrations from a powerful cut. This thoroughly optimises the blade for cutting power.
At the sacrifice of durability. Sharpness requires hardness, and with hardness comes brittleness - only a harder material can cut a softer material. Katana are simply not designed to take the same level of abuse as Western swords. An extremely hard edge would be prone to chipping when parried or striking metal armour.
A thick wedge shape also must move more material aside to cut through something. Armour is made out of hard or rigid materials, so the katana-cut is attempting to force aside metal or cuir-bouilli which refuses to bend. So an edge sharp enough to cut the armour would still not create a sufficient gap for the rest of the blade to cut the person beneath it (specialist techniques against armoured opponents supports this - clearly the 15thC Japanese did not believe their swords cut through metal armour).
Personal opinion: For my taste, the cutting power is superfluous - Western swords can consistantly cleave all the way to the bone, even through it. That cut would disable or even kill a foe, I see no compelling reason to sacrifice other advantages to cut deeper.
Second personal opinion: Most skilled professional fighters will wear armour, having a sword weak against armour is a disadvantage against the foes who pose the most threat.
Most of what I know of katana handling is quick-flowing with power from rotating the grip and pushing the hips. Pulling a curved blade in this way makes it slice as it shears. The footwork is mostly linear with short quick hopping or even shuffling steps. There are also lots of references to a close-in "counter-cutting" style.
Side note: Popular Samurai weapons were tanto daggers used for finding gaps in armour while grappling. They also favoured the yari (spear), diakyu (bow) and naginata (a type of polearm).
Japanese Armour:
The main difficulty with this research is the language barrier - the different styles of armour are difficult to tell when so many terms refer to pieces of armour.
Also, contrary to some beliefs, Japanese armour was not made from bamboo. Some armour designs were similar to the katana with both extremely hardened metal and springier metal.
I know of 3 major designs. I will be using Western terms.
Design 1, Lamellar - Overlapping metal scales or plates tied together with either silk cords or leather. Offers excellent protection against edged weapons while allowing good freedom of movement. The lames (small scale-like plates) were deliberately arranged to overlap upwards, so a foe must stab downwards to fit the point of his weapon where the lames overlap - which is impossible for a foot-soldier fighting a mounted samurai.
Mostly this is used for a cuirass (torso), as the lacing is not flexible enough for limb-movement and difficult to keep from sliding down. The main disadvantage of this armour is the extensive cloth lacing when soaked in water and mud became twice as heavy as it normally was, was slow to dry, and created a perfect breeding ground for vermin. Marching through mud, and without access to baths for weeks or months, was an easy way to die of disease.
Design 2, Lacquered leather - Lacquering leather makes it harder and more rigid. While the strength is less than metal, the hardness and rigidity is much the same as wood. A strong direct hit will breach it but a light slice or indirect cut will be deflected. Often the lacquering was brightly or menacingly coloured.
This can cover nearly all of the body, was often the limb-pieces of a warrior in a lamellar cuirass. The lacquering also makes the leather soak up less moisture.
Design 3, Armour of Bands or Splints - Accomplished through lining the inside of a cloth or leather garment with metal plates. This explains some of the 'bulges' in samurai armour, which are pockets for the metal plates sewn onto the inside. Some designs use rivets for the same effect. The leather garment could be brightly lacquered as well.
'Splint' armour is made of long metal strips affixed onto a cloth or leather backing, typically used to protect the limbs.
These are only native armours. Nothing stops a samurai from taking Western armour.