In the game of Diplomacy you will take control of one of the 7 great powers in Europe during World War 1 with the objective to conquer the most strategic supply centers in a given amount of time/turns. But here's the catch, all units you control have a strength value of 1 and you must have a higher attack value to dislodge other players' units in their territory meaning you will likely need to secure support from another nation to complete your conquests. That is where the "Diplomacy" comes in as you will negotiate for support, alliances, establish demilitarized zones, or even stab former allies in the back to secure your objectives and the best part of the game is anything you say or "agree" upon with another player is non-binding.