Diplomacy is a strategic board game created by Allan B. Calhamer in 1954 and released commercially in 1959. Its main distinctions from most board wargames are its negotiation phases (players spend much of their time forming and betraying alliances with other players) and complete absence of luck. Set in Europe just before the beginning of World War I , Diplomacy is played by seven players, each controlling the armed forces of a major European power. Each player aims to move his or her 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.
It's basically an online, browser version of the board game. It's full of backstabbing and betrayals until someone finally emerges as the victor. You can join however number of games you want since everybody makes their turn their leisure so a single game could last for quite a while.