[PvK]

I assume it is both the katanas and the armor.

I have done very well with samurai, though I tend not to use samurai archers with melee samurai, because then most of my samurai casualties end up being from friendly fire! Since samurai don't use shields, I make sure I have a missile screen of fodder in front of them, and don't shoot into my own forces (I use separate armies of samurai archers, kind of like how I never put arbalests or crossbows with my Ulmish infantry).

I think a good Production scale and fort construction is the way to go for a Jomonese samurai army.

PvK