In order to cut through a shield of bronze (which I really doubt because bronze is an alloy itself, so it is very hard metal), the swing that the samurai has to do will leave him wide open to any attack. Historically, Spartans fought with many armies with different swords and weapons and they defeated them. Actually, in this forum we can see how people are in my opinion bad informed. For example, Korean soldiers developed a very similar sword (kagum) it is as powerful and fast manageable as the katana, but why it’s no so popular? Because katana belongs to Japan, and Japan it’s a commercial power. Samurai is more a publicity thing than anything; and they never, never in history, a samurai defeated any different army besides another samurai army. In the other hand, Spartans were proven once and many times, that they technique, training, style, or whatever you want to call it was superior to many others, including the Persia Army, and they had horses, arrows, and a huge army. The Spartans fought 3 to 1 (S: 10,000 vs. P: 30,000).