I've often spouted the virtues of the katana (just how I got into those conversations to start with is something of a puzzle, now I look back on it): the dedication of its craftsmen, the sharpness of its blade, and its ability to cut through all sorts of unlikely things...
However, apart from what I've heard on the TV and radio, it turns out I'm not really all that clued up on the "mighty" katana.
It wasn't until I happened upon this video that I realised the limits of my education in sword-crafting (which, as you might imagine, are very limited).
The guy makes some excellent points; most of the dirty-work on a Japanese battlefield would have been done with the spear or other weapons, and the functional aspects of the craftsmanship that went into the swords was in no way unique to Japan.
The first point I should really have been aware of from Jansen's "The Making of Modern Japan", and other things I've read. As with Europe, technological advancements often came in the form "if we've got a longer spear than the enemy, we'll be able to hit them before they can hit us", and alongside firearms, the spear was a staple of weaponry as the warring kingdoms period drew to an end.
That said, I'm certain that if you're a foot soldier with a massive pike, and concentrating on hitting the enemy in front of you, several hundred men in heavy armour wielding katanas running into your flank is going to ruin your day.
What confuses me about historical Japanese warfare is the failure to adopt the shield. Even a katana is going to stop against a well made shield, and while you block the blow, you could be eyeing up your opponent for somewhere to stick your own short-sword. A quick search on internet forums suggests that the lack of shields was down to 1) lack of supply of metals, 2) the historic preference of samurai for horse archery [which kind of precluded the use of a shield], 3) the possible lack of honour associated with hiding behind a shield, 4) the Japanese armour plating, particularly on the shoulder (the sode), was functional as a small shield. 5) "shield? You must be referring to the peasants"
which of those reasons are actually relevant, I've no idea. number 4 seems somewhat dubious to me, as I've never seen a sode large enough to be really protective; there always seems to be an opening in the armour around the elbow joint. Plus how are you to deflect blows below your waist? You'd have to use your sword, which makes counter attacking more difficult...
That said, my weapons of choice would be the firearm with a katana as back up. Or, if I'm lucky the commander will decide to simply not fight.
EDIT: Oh, and for what its worth, I actually own a katana. Considering I only paid 70 quid for it, I'm guessing its not authentic, but it looks cool, and lets face it, that's the only reason you're going to own a sword these days... I hope...