Broadly speaking, the Chain Mail man-to-man melee combat system presents two kinds of weapons, those that can be wielded with one hand, and therefore in combination with a shield, and those that require two hands, meaning that the combatant must forgo such protection. A two-handed sword will generally score a kill on a 5+ or a 6+ on 2d6 with only plate armour and shield requiring a 7+, whilst a halberd requires an 8+ to achieve the same. By contrast, a one-handed sword requires a 10+ to score a kill against a plate armoured combatant and an 11+ if that same opponent bears a shield. However, the difference in weapon classes makes a big difference in what initially appears to be a relatively clear cut advantage. Because the one-handed sword is class 4 and the two-handed sword is class 10, a fighter wielding the former weapon has three options after the initial round. He can choose to attack twice, once before and once after his opponent with a two-handed sword (or, indeed, halberd); he can choose to reduce his opponent’s roll by 2 and attack after him; or he can choose to attack first and reduce his opponent’s roll by 1. The net result being that the weapon combinations are roughly equal, depending on the situation. However, the mace is the better choice, requiring only a 7+ to hit a plate armoured target and never needing more than the sword to hit any other class of armour.
This interestingly balanced system was largely thrown out for the alternative Dungeons & Dragons combat system, and by all accounts was never used by Gygax in the context of his own campaign. It is not hard to understand why, given that the man-to-man system was not written with monsters in mind and that the fantasy combat table was not designed to accommodate groups of heroes. However, in reducing all weapons to doing 1d6 damage and having a hit chance based on the fighting ability of the attacker, the alternative combat system made two-handed weapons redundant. A character could either use a one-handed weapon and shield, improving his armour class by one and doing 1d6 damage, or he could use a two-handed weapon, improving his armour class by none and doing 1d6 damage; not a particularly difficult choice. The Greyhawk supplement attempted to rectify this by introducing variable damage dice for weapons, and a weapon type versus armour class modifier to the attack roll. The solution was overcomplicated for the task at hand, which really only called for a +1 to hit for two-handed weapons, but it was probably seeking to address a wider range of interconnected concerns that had developed over time.
Notably, the Advanced Dungeons & Dragons combat system builds on the Greyhawk solution as well as incorporating bits and pieces of the Chain Mail man-to-man rules. One major innovation, though, was the introduction of a seemingly innocuous rule for fighting with two weapons, allowing characters to use a dagger or hand axe in addition to their primary weapon. A character utilizing this technique suffered a −2 to hit with his primary weapon and a −4 to hit with his secondary weapon, but the penalties could be mitigated to as low as 0/−1 if the character had a high enough dexterity. More significant as a balancing factor was that the dagger and hand axe had fairly poor modifiers versus armour. On the surface, this meant that the design of the game encouraged using two-handed weapons against large or heavily armoured enemies and fighting with two weapons against more lightly armoured small or medium opponents, whilst a one-handed weapon and shield combination occupied the ground between them. In practice, many game masters ignored the optional weapon type versus armour class table or failed to apply it to monstrous opponents, and perhaps more importantly many players recognised fighting with two weapons for what it was, a force multiplier.
Once it was realised that the associated penalties for fighting with two weapons were vastly outweighed by the potential advantages, the exploitation became obvious, particularly at higher levels where the modifiers to hit could be combined from many sources. The second edition of Advanced Dungeons & Dragons took a much needed step towards reducing the potency of the technique in the default rules by explicitly limiting a second attack to one per round and preventing the doubling of attacks occasionally inferred from the first edition rules. However, the simplification of the weapon type versus armour class rules undermined the advantages previously enjoyed by two-handed weapons and removed the disadvantages that had been placed on secondary weapons. The simultaneous release of the Complete Fighter’s Handbook, authored by Aaron Allston, compounded these problems, making it possible to mitigate all the penalties associated with fighting with two weapons and allowing any one-handed weapon to be used in a secondary capacity. Allston also identified four fighting “styles”, or techniques, labelling them “single weapon”, “weapon and shield”, “two weapon”, and “two hander”, but they were less than equal.
Although the techniques were not equal, they required a significant expenditure of character building resources to acquire. A character specialising in single weapon technique could improve his armour class without a shield or secondary weapon by one for one proficiency slot, and by two for two proficiency slots; not a great deal when using a shield the first benefit is gained for free. A character specialising in two-handed weapons reduces the speed factor of the weapon by three and gains a +1 damage bonus when wielding one-handed weapons two-handed; so no reason at all to ever really choose the bastard or two-handed sword over the long sword. A character specialising in weapon and shield technique is able to attack with his shield as though fighting with two weapons for one proficiency slot, and reduce the penalties for doing so to 0/−2 by expending two proficiency slots, though when he does so he forgoes the improvement to armour class he would otherwise enjoy from utilising a shield; far better to invest one proficiency slot in two-weapon fighting and be able to use any weapon in a secondary capacity at a 0/−2 penalty, and switch between the two techniques as the situation demands.
The Player’s Option series and, as I understand it, the Birthright campaign setting took the idea of style specialisation even further, for example introducing the “shield proficiency”, which allowed fighter to expend one proficiency slot to improve the armour class bonus from a large shield by two, making it an instant sine qua non. Of course, D20/3e rather overreacted to the legacy of fighting with two weapons and the mid edition revision turned two-handed weapons into its successor. It is often noted that in actual play the underlying mathematics are not noticed or have less importance than as theoretical design elements, but the more robust the system the more likely it is to avoid breaking down in other areas. So, for your entertainment and convenience, here are my current campaign rules for fighting techniques along with a few combat actions for use with OSRIC. Obviously, some of these ideas will find their way, or have already found their way, into Astonishing Swordsman & Sorcerers of Hyperborea.