Who says B/X’s 40th anniversary says Chainmail’s 50th. Before there was “the game that started it all,” there was the game that started that. Initiated by wargamer Jeff Perren and further elaborated by Gary Gygax, iterations of the rules for medieval miniatures wargames were published in zines as early as 1970.
Just prior to its 1971 publication by Guidon Games, Gygax added 14 pages of rules inspired by fantasy fiction. The “Fantasy Supplement” opened the gates on tabletop battles with wizards and heroes, elves, trolls, giants, and other fantastic and mythical creatures, including dragons. Chainmail was the steel with which Dave Arneson struck Wesely’s Braunstein flint. The spark was Blackmoor, and it ignited the flame that became DUNGEONS & DRAGONS.
“Valormr: val (war or slain) + ormr (wyrm), pronounced Val-ORM-r. During the Throrgrmir Renaissance, when the new-hatched wyrmlings prowled the dungeon, already dragons came to hasten the prophesied Age of Dragons. The dwarves called to their neighbors, who responded in force. Dragons recruited forces of Chaos to oppose them.”
—from “Empire of the Undersun”
For the history of D&D, see Playing at the World (Jon Peterson, San Diego: Unreason, 2012) and Designers & Dragons: The ’70s (Shannon Appelcline, Silver Springs, MD: Evil Hat, 2013).