Less Than THAC0

Thac0 was a part of AD&D?  Seriously?  Because I played AD&D (1st ed.) for a long time and wasn't aware of it.  Thanks to Cyclopeatron's research, I now know that Thac0 actually predates AD&D--or at least the DMG--but unless you were a computer nerd at UCLA in the late '70s, my guess is you probably didn't know why Thac0 was listed in statblocks for NPCs in the occasional module or what that unexplained column of numbers in Appendix E of the DMG labelled "To Hit A.C. 0" was all about.

Indeed, pointing to Appendix E as proof that Thac0 was a part of AD&D is like saying that "Less than Zero" was a Brad Pitt movie.  Sure he was in it--according to Imdb he was an uncredited partygoer--but it's only on because 2e adopted Thac0 full on--or so I gather--that this gains any significance at all.  If 2nd edition AD&D had gone with ascending ACs and to hit bonuses more akin to Castles & Crusades, et. al., Thac0 would be as familiar to us today as all those other party-going extras who did not become Brad Pitt. 

Thanks, but what's my Thac0?

Just as Andrew McCarthy, James Spader, and Robert Downey jr. were the headliners in the 1987 film of extreme LA youth decadence while Brad Pitt was an as yet unknown--except, perhaps, to a handful of "Growing Pains" devotees--the combat matrices on page 74-75 were the stars of the AD&D combat system.  When Aggro the Axe and Gutboy Barrelhouse squared off in the sample combat narrative on page 71 of the DMG, they used the combat matrices on the following pages to determine the success of their attack rolls, not some goofy acronym.  The continued absence of Thac0 rules in 1985's Unearthed Arcana is further indication that Thac0 was still not a significant part of AD&D, or had yet to be officially sanctioned by TSR anyway.

But obviously the Appendix E reference indicates that there was something going on with Thac0.  But did anyone outside of a posse of computer science majors at UCLA and a few Lake Geneva insiders actually know what Thac0 was supposed to be used for?  As a kid, I assumed that it was listed to give a measure of relative combat acumen--just as AC is a measure of defensive capacity--that could, in a pinch, be used to recreate the combat matrices.  Why anyone would bother doing such a  thing was beyond me since the matrices were readily available on every DM Screen that ever partitioned a gaming table.

But I could be totally wrong.  My sample size is not large; maybe loads of people were using Thac0 back in the day, despite TSR's refusal to endorse it.  Is there anyone out there that was into Thac0 before it went mainstream?  And what was the first TSR publication that actually explained what Thac0 was all about? 

THAC0?

Recently I came across some new schoolers at Penny Arcade comparing old school D&D to the version they play; they called it 4E or Double D or something.  Hey, I'm just an unfrozen caveman, I don't understand these ascending armor classes or... well, that's pretty much all that I know about ND&D,* so I'll stop there.  Seriously, it does not ruffle my feathers at all that there's a new version out there that's completely different from and incompatible with the game I played before the ice age claimed me back in the late 80s.  Heck, I wanted to change that game too, can't blame TSR et. al. for doing the same thing and making money off of it.  If the kids are havin' fun, then Game On!

*ND&D=New D&D, commonly denoted by a numerical "e rating," the higher the e-rating, the newer the D&D.

But there is one piece of information that I'd like to impart to the younger generations, and it's this: THAC0 and descending Armor Class are NOT synonymous.

Despite what this guy seems to think, if you mention THAC0 to stick-in-the-mud old schoolers like me who never graduated from the Gygax-authored tomes, there is no reason to expect them to know what you're talking about.  Though the term Thac0 might have existed back in the day, it was not at all relevant to the game as it was played on the streets.  The term came about, according to some research I poached from Philotomy (sadly, that blog is no longer with us), because of a curious column of data in the monster listings (Appendix E) of the AD&D Dungeon Masters Guide that was labeled "To Hit AC 0."  However, there is no explanation of the significance of this this item and one is left to wonder why it was included with the other, more pertinent stats listed.  Indeed, there's no reason I can see why they chose to spend 19 pages rehashing info that was already available in the Monster Manual when the only real value this table offers is looking up the XP value of that Shedu your players just blasted into a heap of fur and feathers (1,950 + 14/hp).  No, when we old schoolers wanted to crush our foes we didn't call out our thac0s like a battle cry and have at it with our 20-siders; we turned to the combat tables on page 74-75 or eyeballed the DM's Screens that grew like stands of alder trees on gaming tables throughout the land.  Then we walked 14 miles to school through a blizzard, uphill each way.



Seeing as Unearthed Arcana (1985) was the last new TSR-published D&D product I bought--though I played on for a couple more years in isolation from the machinations of Lake Geneva--I'm not entirely sure when thac0 grew to predominance.  In fact, I wasn't aware that it had gained any traction until I read the Penny Arcade post referenced above.  I'm guessing that it became prevalent in the 2nd Edition of The Game as a means to replace the combat tables as the go-to source for 20-sided slaughter in AD&D, a move in which I can definitely see some value.  And presumably some game mechanics were changed somehow (I'm looking at you, repeating 20s) to make it more usable as a system.  I'm not here to preach about the superiority of any one combat system over another--though, as much as I like the descending AC aesthetic, the ascending AC system sure makes life easier--but kids, get your facts straight.

Epilogue:
So, yeah, I lived most of my life without giving Thac0 any thought whatsoever until these meddling kids started confusing descending AC values with this eldritch acronym.  But now that my dander is up, why did they make it Thac0 and not Thac10?  AC 10 is the Absolute of descending ACs; like 0 degrees Kelvin, you could only go up from there.  And since no one needed a 20 to hit AC 10, you didn't need to worry where you stood on the ledge of repeating 20s.  It does rhyme with the name of a major college sports conference of the western U.S., but that will likely be changing soon anyway.  [Let's just say that Wazzoo won't be sandwiched between 2 filler helmets down at the bottom for much longer.  Though the Cougs are certainly likely to stay at the bottom.]

Some have argued about the zero providing balance whereas using 10 as the base seems arbitrary and provides opportunity for unlimited growth and, therefore, AC inflation.  I can sort of see what they're getting at; but unless you're in a game where there is a likelihood of finding suits of +12 plate mail or +24 rings of protection, there are probably de facto limits to AC inflation already in place. 

Go Beavers!