A program called Diplomat for playing Diplomacy (a seven-player board game) is described, It is very different from programs that play two-person zero-sum board games (such as chess or checkers) since it must act in an uncertain environment, it must decide on intermediate goals and explain those to potential allies, or hide those from them. Diplomat is able to make proposals to other powers and can also receive proposals and answer them. In case a player suggests a plan, Diplomat must evaluate it and react accordingly. It must also evaluate the relations between the other players in order to detect potentially dangerous coalitions. Diplomat uses a set of domain-specific heuristics. The experience shows that Diplomat plays in a way that is hard to differentiate from play by humans.