A play-by-mail game is a game played through postal mail, email, or other digital media. Correspondence chess and Go were among the first PBM games. Diplomacy has been played by mail since 1963, introducing a multi-player aspect to PBM games. Flying Buffalo Inc. pioneered the first commercially available PBM game in 1970. A small number of PBM companies followed in the 1970s, with an explosion of hundreds of startup PBM companies in the 1980s at the peak of PBM gaming popularity, many of them small hobby companies—more than 90 percent of which eventually folded. A number of independent PBM magazines also started in the 1980s, including The Nuts & Bolts of PBM, Gaming Universal, Paper Mayhem and Flagship. These magazines eventually went out of print, replaced in the 21st century by the online PBM journal Suspense and Decision.

Diplomacy is a strategic board game created by Allan B. Calhamer in 1954 and released commercially in the United States in 1959. Its main distinctions from most board wargames are its negotiation phases and the absence of dice and other game elements that produce random effects. Set in Europe in the years leading to the First World War, Diplomacy is played by two to seven players, each controlling the armed forces of a major European power. Each player aims to move their few starting units and defeat those of others to win possession of a majority of strategic cities and provinces marked as "supply centers" on the map; these supply centers allow players who control them to produce more units. Following each round of player negotiations, each player can issue attack and support orders, which are then executed during the movement phase. A player takes control of a province when the number of provinces that are given orders to support the attacking province exceeds the number of provinces given orders to support the defending province.