Henry Bodenstedt created the medieval wargame Siege of Bodenburg in 1967. This game was designed for use with 40mm miniatures and served as the foundation for later developments in the genre.
First edition Chainmail saw print in March 1971. It quickly became Guidon Games' biggest hit, selling one hundred copies per month.
The fantasy supplement included mythical creatures such as elves, orcs, and dragons along with heroes, superheroes, and wizards. It also added concepts like elementals, magic swords, and spells including Fireball and Lightning Bolt.
The Chainmail cover art was inspired by a Jack Coggins illustration from his book The Fighting Man: An Illustrated History of the World's Greatest Fighting Forces. The fantasy supplement illustration of a mounted knight charging towards a dragon was drawn by Don Lowry based on an illustration by Pauline Baynes.
The game served as the foundational rulebook for Dungeons and Dragons which eventually surpassed its parent in popularity. Gary Gygax wrote in the June 1978 issue of The Dragon that players played primarily without miniatures for the first two years before Swords and Spells was added as a rules supplement in 1976.
The mass-combat rules were intended for a 1:20 figure scale where each figure represents twenty men. The man-to-man combat rules utilized a 1:1 figure scale while the fantasy supplement also included rules for 1:10 figure scale battles.