Rules of Combat

White Box Combat Options
Vol. I Men & Magic refers to the Chainmail fantasy rule(s) regarding combat as well as offering the "alternative system" which has become the game's standard combat methodology. Chainmail and the LBBs offer a number of combat resolution methods and conceivably, all of them may be used by the referee at various times for various effects during combat in the game.
The Chainmail rules cover a number of wargaming situations including a combat resolution system for tabletop miniatures battles using one figure to represent several men. A standard "scale" of wargaming is 1:20 where each figure represents 20 actual men. Chainmail resolves this 1:20 combat by throwing one to four d6 per figure and looking for a target score. (It's a bucket of dice mechanic.) The man-to-man melee rule involves casting two d6. Both systems involve a table, one that matches attacker troop type verses defender troop type in the case of the 1:20 rules or weapon type verses armor type in man-to-man melee. The latter system probably influenced the Advanced Game weapon type "to hit" adjustments.
The Fantasy Supplement combat table is most similar to the man-to-man rules and involves a matrix for attacker by type. Types include various fantasy creatures as well as Hero, Super Hero and Wizard. Rolling two d6 produces a number which is compared to the target number and gives a result of Killed (roll exceeds target #), Fall Back (roll equals target) or No Effect (roll is under target). It is interesting to note that in Vol. I Men & Magic, the Statistics Regarding Classes table refers to fighting capabilities including Man, Man +1 etc. and supposedly refers to the Fantasy Combat Table in Chainmail where there is no listing for "Man". I presume that would indicate use of the man-to-man table or could refer to the 1:20 system where the plus could indicate additional d6(s) to be rolled.
Chainmail also offers Jousting rules and a Jousting Matrix which I find useful when using castle encounters found in "off-hand adventures" as described in Vol. III The Underworld & Wilderness Adventures. The adventures of a knight errant breaking lances and testing him(her)self against the world is quite romantic and may appeal to certain players.
Vol. I Men & Magic introduces the "Alternative Combat System" using a d20, armor class and class level which is often referred to simply as the d20 system. Again a matrix is used comparing class level (or monster hit dice) to armor class to produce a target number which must be equaled or exceeded on a d20 roll to produce damage. Damage is a single d6 score and is deducted from Hit Points. This is the combat system which has become standard for all subsequent versions of the game.
Combat, or conflict between PCs and beings and creatures found in the imaginary environment of the game, is at the core of White Box (and later editions). Once the players decide their characters will fight with rather than run from, parley with, or trick their tabletop opponents in order to win treasure (and experience), the referee has a number of options for adjudicating the resulting combat. Conflicts may be fought involving relatively large numbers of combatants as the PCs lead various troop units in tabletop battle using miniature figures or smaller engagements can be resolved using the man-to-man or fantasy rules. A knightly joust is also an option to test one's mettle on the field of honor (and thereby impress the damsels!).
Few later versions of fantasy adventure rules offer as many options as White Box. I see each of the combat systems as a tool which can be chosen by the referee. The ability to slow combat down, make it more detailed and dramatic, or speed it up and showcase the superpower of higher level PCs and their ability to slay many low-level adversaries gives the referee a nice option. While relying on a single combat mechanic has the advantage of allowing players to more easily predict the nature of any conflict, having choices gives the referee an opportunity to perhaps achieve different effects through combat during play. Having options is one of the many reasons I enjoy White Box.