Saturday, November 5, 2011


In the course of a discussion of D&D tactics, it was brought up how in old school D&D the closest equivalent they have to "flanking" like in 3.5e is a thieve's backstabbing.  While I'm not sure the analogy is necessarily the best, it got me thinking about what the most effective use of backstabbing is.  For a thief to backstab, they have to use both their "Move Silently" and "Hide in Shadows" ability to move behind their target.  Because the probabilities multiply, a quick calculation reveals that this is a high-risk endeavor for any thief. Following the Labyrinth Lord rules, a first level thief has a less than 3% probability of successfully backstabbing, and no thief stands greater than 50-50 odds until he is 10th level.  Given that, my intuition is that the payoff for backstabbing is on average fairly low.  I'd only recommend thieves choose to backstab in the face of a real risk of total party kill (TPK).  To say more would require more modeling, though.  Since I'm already behind on my Markov model for my elf versus an orc, it's probably best that I hold off on going much further on this one.


  1. Hmm...hide in shadows or move silently, unless the thief is approaching from the front then he needs both. You don't have to hide in shadows if you approach from behind, because your target can't see you, and you don't have to move silently if you are hiding in shadows because your target is coming to you and not you to him.

    Surprise success generally is assumed to allow a thief to backstab. Moving silently and hiding in shadow increase a thiefs chance for surprise. Normally 1-2 in d6 is increased to 3 in 6 or 4 in 6 if both HS/MS are successful. Even if both fail, the thief still has a 33% of surprising his foe, which is much higher than the 3% you propose in your post!

  2. The 3% is from a strict reading of the rules. I like your idea, though. I'm also cautious about it, though, because I don't like the idea of a thief turning into a combat-oriented class. I think of them more as spies, scouts, and occasionally raiders. Ultimately, though, their first instinct should be to run rather than slug it out.

  3. A 'strict reading' of the rules means a 1st level fighter in plate armor has a higher chance of surprising his foe (1-2 in 6 or 33%) than a 1st level thief 3%.

    1. I disagree. Surprise is determined by side and applies universally, hence both a fighter and a thief have the same odds (33%) of surprising another side. None the less, according to the rules whether a surprise check occurs is up to the DMs discretion. That might mean a thief suddenly appearing from a concealed position (not necessarily in shadow or by moving silently), or a fighter in armor bursting through a door.