Leave it to the highly knowledgeable folks at DragonsFoot forums to have the gooey details.
I said THAC0 was introduced in AD&D 2nd Edition. WRONG.
This, my friends, is why one should corroborate their sources before publishing information.
I saw a thread discussing THAC0 in the DF forums tonight and thinking myself knowing something, I got egg on my face. The conversation went thusly...
"Then they don't know their D&D history.To which I replied,
I put THAC0s in modules R1-4 (1981-82) and I got the term from local games in Lake Geneva.
It goes back to the beginnings of 1e or even earlier.
I don't know how far it goes back for sure. I think I recall it being posted somewhere that THAC0 was as introduced with Unearthed Arcana, but I can't say for sure myself. I'm guessing kind of a AD&D 1.5 thing maybe?
I do know that as i sit here with my Advanced Dungeons & Dragons circa 1979 (9th printing 1987) Dungeon Masters Guide that THAC0 is not mentioned in the Index of the book, it is not mentioned in the "Armor, Armor Class, & Weapons" section of the book (pages 27-28) nor is it referenced on the "Combat Tables" (pages 74 - 75).
BTW, I'm not trying to be contentious, just historically accurate.
And here's where I got sent to school...
Thac0 is right in the 1e DMG (page 196-215 in the monster summaries, with a column for "To Hit A.C. 0").
All I could say was,
Yup. there it is. I've seen it hundreds of times and never really paid attention to it. never used it once.
I stand corrected.
I wonder if I never paid attention to it because while it's included on the table, I never seemed to find it discussed in the book anywhere, thus rendering it forgettable to me.
The fella was absolutely correct. THAC0 has been in AD&D 1st Ed since 1979. However, though as I mentioned in that forum discussion, all I ever saw of it was it's listing in the Monster table and nowhere else.
It seems didn't get brought out into the sunlight until 2nd edition to make it more plain. If I'm wrong about that, please feel free to comment here and correct me on that too.
Of course, this doesn't change how THAC0 in terms of I still don't plan to use it.