In 1967* Wesely served as referee for a Napoleonic wargame set in the fictional German town of Braunstein. As usual, two players acted as commanders of the opposing armies, but because he was interested in multi-player games, Wesely assigned additional, non-military roles. For example, he had players acting as town mayor, banker, and university chancellor. When two players challenged each other to a duel, Wesely found it necessary to improvise rules for the encounter on the spot. Though Wesely thought the results were chaotic and the experiment a failure, the other players enjoyed the role playing aspect and asked him to run another game.
Wesely thus contributed to the development of RPGs by introducing: (1) a one-to-one identification of player and character, and (2) open-ended rules allowing the players to perform any action, with the result of the action determined by the referee.
[*] 1969: Tresca, Michael J. The Evolution of Fantasy Role-Playing Games. McFarland & Company, 2001. p60.
From Wikipedia, David Wesely, The Braunstein Game. Available under the CC-BY-SA license: