In the early 1970s, Gygax was heavily involved in the wargaming community, designing and publishing several wargaming rulesets. He also founded a wargaming club in Lake Geneva, Wisconsin, which was frequented by Arneson. Arneson had created his own wargame based on naval combat, but he found that he was more interested in the individual characters rather than the ships.

Together, Gygax and Arneson began developing a new game that focused on individual characters and their adventures in a fantasy world. They drew inspiration from a variety of sources, including J.R.R. Tolkien's The Lord of the Rings, Robert E. Howard's Conan stories, and Fritz Leiber's Fafhrd and the Gray Mouser tales.

The first edition of D&D was published in 1974 by Gygax's company, Tactical Studies Rules (TSR). The game quickly gained popularity and spawned a subculture of gamers who were passionate about creating and playing in their own fantasy worlds. Over the years, D&D has gone through several editions and remains one of the most popular tabletop role-playing games of all time.

In 1983, Games Workshop released the first edition of Warhammer Fantasy Battle, a tabletop wargame that featured armies of miniature figures battling each other on a battlefield. The game was heavily influenced by the works of J.R.R. Tolkien, as well as the historical battles of medieval Europe. Over time, Warhammer Fantasy Battle developed its own unique lore and mythology, with a vast array of armies and factions battling for dominance in the fantasy world of Warhammer.

In 1987, Games Workshop released Warhammer 40,000, a science-fiction tabletop wargame set in a grimdark future where humanity is locked in an eternal war against alien races and chaos gods. The game drew inspiration from a variety of sources, including the works of H.P. Lovecraft, the movie Aliens, and the dystopian visions of George Orwell and Philip K. Dick. Warhammer 40,000 quickly gained a dedicated following and became one of the most popular tabletop wargames in the world, with an extensive range of miniatures, novels, and video games expanding on its rich lore and mythology.