amor with armour

[reverancepavane]

I was quite amused to discover that I'd been playing D&D wrong all these years. The exact culprit is how the bonus due to magic armour should have been applied during the game. In Monsters & Treasure it states: "ARMOR: Armor proper subtracts it's bonus from the hit dice of the opponents of the wearer. If the shield's bonus is greater than that of the armor there is a one third chance that the blow will be caught on the shield, thus giving the additional subtraction." What we did was the same thing as for magic swords, and subtracted the bonus from the chance to hit. Now this is effectively equivalent, since the Attack Matrix II: Monsters Attacking (in Men & Magic) is divided into columns 2 Hit Die in width, with the probability of a hit occurring (typically) decreasing by 2 per column. Thus the probability of a hit occurring is effectively reduced by 1 per Hit Die of a creature. No effective change there. The interesting bit is when you shift to Attack Matrix I: Men Attacking, where the columns are divided by level according to class: fighting-men have columns that are 3 levels wide, clerics are 4 levels wide, and magic users are 5 columns wide, again with the probability of a hit typically reducing by 2 for each increase in the column. However since it requires a greater bonus to give a column shift against a magic user, it is plain to see that magic armour is less effective against magic users. <grin> Incidentally, the rows of the two "Attack Matrices" were divided by the type of armour worn (platemail, chainmail, leather and none, with and without shield), and were given a number to represent this, called Armour Class, varying from 2 (platemail & shield) to 9 (no armour whatsoever). Now the probability of a hit was always reduced by 1 each time you move up a row (or subtracted one from the armour class). This led to two things. The first was the idea of THAC0 (To Hit Armour Class 0), which condensed both attack matrices into a single number to which Armour Class could be subtracted to determine the chance to hit. The second, was that it was simpler to subtract the bonus to the armour from the normal Armour Class of the armour, and then use that number to represent the character;s armour. However in the original game, especially if you used the weapon modifications against armour from Greyhawk, it is plain to see that +2 Chainmail was not supposed to be the functional equivalent of platemail, despite the fact they had the same effective Armour Class. And I don't know anyone that ever used the 1/3rd rule for shields, or the fact that a magic shield was only effective if it's bonus was higher than the armour (and then presumably only the difference would be added).