Updated: Jun 14, 2018
Now that we've talked about segments, surprise should be easy to grasp, since everything that happens during surprise happens one segment at a time. It's like time slowing down during that moment of fear...
I do not always roll for surprise. Many times, cautious scouting by characters gives some hint about the presence of enemies nearby. In these cases, by DM fiat, I rule that the group does not need to roll. It is a reward for taking the exploration seriously and cautiously.
But in at least 50% of cases (probably more) surprise is checked. Using the DMG p. 62 distance checks to determine when to check for surprise is one way of doing it and lends itself to theater of the mind. But if you use minis, common sense is better.
AD&D surprise follows Gary's pattern of using a single die to generate both a boolean and a quality in a single roll.
My character is surprised on a 1 or 2 on a d6. I rolled a 2 (the worst possible result) and am therefore surprised for 2 segments (AKA Completely Surprised).
Clarification: Surprised = 1 segment. Completely Surprised = 2 segments. You will see assumptive references to these terms in both the rule books and various 1st edition modules.
But wait! My awesome (soon-to-be-dead) 1st Edition AD&D character has a DEX of 16! The reaction adjustment of +1 means I get to subtract 1 segment from my surprise state, therefore I am not surprised at all! Woot!
Yes, that is correct.
We can therefore extrapolate that characters with 16 DEX can NEVER be completely surprised. When complete surprise is rolled, the character with 16 DEX is merely "surprised". Characters with 17 DEX or higher are therefore NEVER surprised at all.
This is an important rule because having one or more characters in the party with high DEX mitigates the lethal surprise rules of AD&D and sometimes allows those characters to actually kill one or two baddies in the blink of an eye when both parties are surprised.
Because there are errors in the surprise charts printed in the 1st edition rule books, surprise became difficult to parse. It is actually simple.
But wait! What about situations where the party is surprised 3in6, or 4in6, or the module claims the monster will (100%) attack with surprise?
In these cases you roll two dice. Check the percentage first (3in6 for example) then roll a second d6 to determine surprise:
1 thru 3 = surprise
4 thru 6 = complete surprise
And, in these cases, I would still apply the DEX adjustment from PHB. So when a monster attacks with 100% surprise, that DOES NOT actually mean everyone in the party will be surprised.
See? The party isn't doomed. Probably.
(On a side note, Gary liked to do crazy stuff sometimes like in WG4, where IIRC you roll a d4 to determine how many unanswered attacks the Dire Wolves get on the hapless and thoroughly surprised party. IMO, this is Gary being Gary rather than an insight into how surprise works and the DM is certainly free to say that even characters with an 18 DEX might be susceptible to a segment or two of surprise in extraordinary situations. But on the whole, normally, I just use what's outlined above.)
When you have characters with advantages, like rangers or monks, and the chances for surprise conflict with the situation or monster: E.g. Monster surprises 4in6 but Ranger is only surprised 1in6, you can use the ADDICT conversion if you like (though I insist ADDICT is wrong about there being more than 2 segments of surprise) or to the spirit of the law, you can simply ballpark the advantage.
Example: Since normal surprise is 2in6, the ranger has a 16% advantage. Instead of surprising 4in6, the monster will surprise only 3in6. This is in the interest of speed of play.
Circling back around on ADDICT, the only time I'd rule that there could be MORE than 2 segments of surprise is when the character's DEX is so low that it actually adds surprise segments...or (as in the case of the Dire Wolves in WG4: the DM just wants to ensure his monster gets in a few bites before being slain).
In cases of mutual surprise, simply handle it one segment at a time. If on the first segment EVERYONE is surprised, no one can do anything and the segment slips by. If on the second segment SOME characters are still surprised but the monsters are no longer surprised, then the monsters get 1 segment to act.
Per the rules, each combatant treats one surprise segment as a full round for attack routines. Spell casting is limited. So you could fire off Magic Missile in one surprise segment and then fire it again after surprise is over: in the regular round. OR, you could start casting fireball while the monsters are surprised for 2 segments, and that fireball will launch at the end of the 1st segment of the regular round.
Tracking this stuff is super easy if you use the combat round tracker from my previous post, which I modified to be clearer and more digestible. You can find it in my DM's Familiar (a Microsoft Excel Spreadsheet w/ a bunch of stuff I use during games). If you open the DM's Familiar, the tab labeled "COMBAT" contains the round tracker.
Hey, Anthony: bet you don't use the rule that you can fire six arrows during 1 segment of surprise!
Well, I have when it was actually applicable (twice in four years) and I know this sounds crazy but it didn't have the devastating impact you'd think it would. The to-hit-AC-type adjustment, coupled with the fact that most creatures only carry around 12 arrows meant that the arrows went out quickly, many of them missed and therefore broke against the walls of the dungeon. True, the other guy got pincushioned; but not in the over-the-top way you'd expect.
End result was that the shooter went from a full quiver to having only 4 (or so) arrows left and the encounter didn't feel any more deadly than regular old 1st edition AD&D.
Still, I wouldn't class this as an intrinsic mechanic. Whereas I would NEVER do away with things like weapon speed factor, or segments, the machine-gun rule for missiles during surprise is something that I think you can take or leave.
Last thing to say about surprise is, don't forget that if the party surprises the monster, there might be other options available than simple combat. Surprise could indicate that the monsters have not even detected the party yet, and won't for an additional X segments. In this case, the party could slip away collectively without raising an alarm. Or they could try something more creative like toppling a nearby statue on a group of orcs that are preoccupied around their camp fire.
I think weapon speed factors will be the next blog post. And yes, we really do play this way. :)