I have mentioned a number of times how much I enjoy the abstract combat system in B/X. To me each individual piece fits together like a puzzle to give a near perfect abstract/narrative combat system that also gives players important tactical options.
Part of this combat system is a distinct lack of modifiers for "to hit" rolls. Taking a quick look through the Character Classes and The Encounter sections of the Basic rulebook gives the following modifiers that can be applied to "to hit" rolls:
- Thieves Abilities (B10): The thieves' "backstab" ability which grants a +4 bonus
- Resting (B19) and Running (B24): if not rested a character will have a -1 or -2 penalty, respectively
- Retreat (B25): opponent can add a +2 bonus
- Range (B26): +1 to hit with missile weapons at short range and -1 to hit at long range
- Cover (B26): -1 to -4 based on how much cover
- And of course Ability score bonuses (Strength for melee and Dexterity for missile attacks) and magical bonuses.
The lack of a multitude of situational modifiers goes hand in hand with the abstract system where one "to hit" roll does not equal one swing of a sword.
It doesn't surprise me that most of the modifiers listed above are related to missile attacks. Missile fire just doesn't fit as nicely into the abstract combat system.