Weapon Types vs. Armor Modifiers (PHB)

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==Weapon Type vs. Armor Modifiers (Optional Rule)==
Not all weapons perform the same. If they did, there would be no need for the wide variety of weapons that exists. Only one form of each weapon type, the most useful one, would be used throughout the world. This is obviously not the case.
Aside from the differences in size, weight, length, and shape, certain types of weapons are more useful against some types of armor than others. Indeed, the different armors and weapons of the world are the result of an ancient arms race. Every new weapon led to the development of a new type of armor designed to counter it. This led to new weapons, which led to new armor, and so on.
In the AD&D game, weapons fall into several categories, based on how they are used. The basic categories are slashing, piercing, and bludgeoning.
Slashing weapons include swords, axes, and knives. Damage is caused by the combination of weight, muscle, and a good sharp edge.
Piercing weapons (some swords, spears, pikes, arrows, javelins, etc.) rely on the penetrating power of a single sharp point and much less on the weight of the weapon.
Bludgeoning weapons (maces, hammers, and flails) depend almost entirely on the impact caused by weight and muscle.
A few weapons, particularly some of the more exotic polearms, fall into more than one of these categories. A halberd can be used as a pole-axe (a slashing weapon) or as a short pike (a piercing weapon). The versatility of these weapons provides the user with a combat advantage, in that the mode most favorable to the attacker can be used, depending upon the situation.
Natural weapons can also be classified according to their attack type. Claws are slashing weapons; a bite pierces; a tail attack bludgeons. The DM must decide which is most appropriate to the creature and method of attack.
Armor types, in turn, have different qualities. Field plate is more effective, overall, than other armors by virtue of the amount and thickness of the metal, but it still has specific weaknesses against certain classes of weapons.
Table 52 lists the weapon vs. armor modifiers applied to the attacker's THAC0, if this optional system is used. To use this table, the actual armor type of the target must be known in addition to the target's Armor Class. The bonuses of magical armor do not change the type of armor, only the final Armor Class.
This system is used only when attacking creatures in armor. The modifiers are not used when attacking creatures with a natural Armor Class.
 Table 52: Weapon Type vs. Armor Modifiers
Armor Type 	Slash	Pierce	Bludgeon
Banded mail 	2 	0 	1
Brigandine 	1 	1 	0
Chain mail* 	2 	0 	-2
Field Plate 	3 	1 	0
Full Plate 	4 	3 	0
Leather armor**	0 	-2 	0
Plate mail 	3 	0 	0
Ring mail 	1 	1 	0
Scale mail 	0 	1 	0
Splint mail 	0 	1 	2
Studded leather	2 	1 	0
:* Includes bronze plate mail
:** Includes padded armor and hides