I started that Katana thing out in response to the discussion on what makes steel. It isn't the other metal alloyed with the iron, it's the carbon.
And yes Japan had to get their iron from iron sands and smelt them with charcoal fires. Their pattern welding techniques produced a magnificent blade, but that was because they had to develop the superior crafting techniques to compensate for their poorer base materials.
Japanese blades have often been compared to Damascus steel, which was also folded. You saw the same type of craftsmanship in Scandinavian weapons, called Uthbert (Supposed to an umlaut over the U.)
I mention this because that last link places comparable steels in the same setting, when the Norsemen fought the English and French. It was the belief that a great warrior's spirit carried on in his blade, so the quality blades weren't scavenged from the battle field, ala D&D. They were bent or broken, and buried with their owner, lest they return somehow.
There's also a tale of King Richard meeting Saladin during the Crusades, one that puts the two styles of weapon in contrast.
It's said that Richard, in a show of strength, drew his sword and hacked through an iron bar in one blow, then challenged the Prince to do the same. Saladin looked at his beautiful scimitar and that iron bar, then drew a feather from a pillow and, after tossing it in the air, swiftly drew his own blade and sliced the feather in half. He challenged Richard to match that feat.
Each type of weapon was well suited to the environment they were made for.
Interestingly, the Japanese blades had a quality that the Saracen blade didn't: A triangular, chisel tip.
My brother, who was into such things, bought a Tanto (Japanese combat knife) at a gun and knife show. While wandering there he saw a man giving a talk on body armor. My brother asked if it would stop a knife, holding out his new purchase. The man said, and I quote, "The human arm isn't strong enough to force a blade through this armor." My brother offered, the man accepted, and he drove the blade through the high end body armor in a single blow. It seems that triangular tip is designed to punch armor, and it works.
Needless to say, the crowd of prospective customers evaporated.
I wouldn't try to slash at medieval armor with a Katana or any of its relatives, but a forceful thrust could surprise a man to death.
Oh, and no knives were harmed in that demonstration.
