[quote=@Agent B52]
This point of yours however was not readily apparent. Rather than a specific set of techniques such as draw cuts, it is the way the katana curves that allows it to cut through flesh and light armour so easily. This is also the reason why various types of sabre and scimitars had curves whenever strong armour for whatever reason was not normally encountered. A good example from the Napoleonic wars is the British 1796 pattern cavalry sabre.

((As a short, humorous aside: The 1796 pattern tended to wound and maim rather than kill. Allegedly the French considered this poor sport and petitioned the British to adopt a more lethal design. The British responds was a more polite form of 'lolno, working as intended motherfuckers'.))

My point is the very issue that made the katana a relatively mediocre sword, namely low quality materials, is the same issue that made it a viable weapon. A katana-wielder was very unlikely to encounter someone wearing full plate. When they did, usually during the invasions of China or Korea, it tended to not end well for them. I am trying to repeat your first point here: Ancient people were not idiots. The katana was invented and came into vogue in a region where it was very unlikely to encounter anyone with a full set of European quality plate armour.
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This is mostly true. However, the point I was trying to make [and evidently failing at. I really should get a second opinion on these before I post them. I am very bad at conveying my own thoughts.] is that the katana is a weapon that developed in a sheltered environment without foreign competition, and while it worked [i]acceptably[/i] for its region, compared to places like europe, where different regions and ideas clashed to thrust technology forward, it stands as mediocre at best.

What I was trying to combat with this post was the unwashed weeaboos who think that 'katana #1 #1 in serbia, katana making album of serbia, katana fast rap serbia' in every single case.

"it is the way the katana curves that allows it to cut through flesh and light armour so easily"

The curve helps in many situations, and is certainly a plus in the very specific environment [killing unarmored, shieldless levies] that it was intended for, but once again: there are much better swords for cutting [the talwar, or other middle-eastern/indian weapons jump to mind], and cutting is highly specialized and usually not useful in broad situations, in contrast to the idea I am trying to disprove.

It should be noted that the katana's curve is much less than many other weapons, both early modern european swords and middle-eastern weapons, and thus lacks many of the benefits the increased curve brings [being able to hold close to the body, additional cutting force, ease of use while on horseback, decreased weight] while still lacking the tapering point and added blade control a straight edge would bring.

Also, I don't know what you count as light armor here. If the samurai lamellar suits, for example, were brought to Europe, they would probably classify as light armor during the times they were in use. If these suits are indeed the things you are referring to, the katana are fairly ineffective, since the katana as mentioned before is a really fat sword, with the curve not helping its efforts, and most lamellar of the time was made of the same metal as the katanas, which would render it very good at stopping blows from the weapon.

"While this is true, there is a difference between weapons optimised for the job. Refer to my earlier point above about the use of armour here."

The katana is optimized for cutting down the unprotected masses and providing a defensive option for samurai in close quarters. My point is that the first goal is relatively easy, and while it does the job fairly well I would argue that declaring a sword 'good' because it is better-than-average at doing the absolute easiest thing a sword can do 'cut through unarmored opponents while both are afoot in close quarters' is not absolutely reasonable.

On goal number 2, being successfully defensive, the blade is curved,decreasing reach and opposing blade control, and the handguard is SEVERELY lacking, which all hurt its ability to keep an unhorsed samurai alive. It also cannot be used easily with a shield while not having the extreme reach of late medieval two handed swords, but since shields were almost completely absent from the Japanese islands this is not particularly relevant.

On my point of 'people in the past were not dumb', the katana is actually the best example I can possibly think of as an exception. The katana remained this way in very large part by the extreme conservatism and religious pressure put on smiths to retain the style and form of the weapon. The clinging to plate harnesses may come close, but I'd still have katanas take the cake.