by E. Sabatine
While very successful as a game, Diplomacy is not a realistic simulation of international relations. The main reason is that in the game players are always invading each other and backstabbing each other with (near) impunity, while in real international politics public opinion limits how often most countries can go to war, or completely turn around their policies.
This variant, entitled "Formal Diplomacy," requires players to pay a price before starting or stopping wars with one another. The mechanisms for this are requirements for formal declarations of war and surrenders before undertaking major actions. These rules should considerably slow down the game, which is why the victory conditions are expressed as a time limit rather than occupation of supply centers. However, they should also increase the tension by forcing players to think hard when choosing their enemies.
The game ends automatically after x number of turns. The player with the most victory points at the end of the game wins.
Players gain one victory point for each supply center they control outside of their home country at the end of each Fall turn, and gain one victory point whenever another player surrenders to them.
Players lose one victory point for each supply center inside their home country another player controls at the end of each Fall turn. They also lose one victory point whenever they declare war on another player, whenever they surrender to another player, and whenever another player occupies one of their spheres of influence.
A player may declare war on another player by writing "Declare War On (Country)", or "DWO (Country)" in the orders. Once this happens a state of war exists between the two players, and does not end until one surrenders to the other.
Players in a state of war may not directly contact or talk to the players they are at war with. However, a player must be in state of war with another player in order to attack the latter's armies and fleets, or to move into the latter's controlled provinces. A player not at war with another player may still support attacks against the latter's units.
A player may end a state of war with another player only though surrendering. This is accomplished by writing "Surrender", "SUR", or "Uncle!" in the orders.
A surrender automatically applies to ALL the players the surrendering player is at war with. A player who has just surrendered is in a state of war with no one. A player who currently controls one or more of the home provinces of a player the former is at war with may not surrender.
Spheres of Influence:
A player may declare that a province is a sphere of influence by writing "Sphere of Influence (Province)", or "SOI (Province)" in the orders. To do so, either one of that player's armies or fleets must have occupied the relevant province, or one of that player's armies or fleets must have occupied a province adjacent to the relevant province and the latter must be vacant, at the beginning of that turn.
An army or fleet used to declare a sphere of influence can take no other action that turn. Sphere of Influence declarations can be supported, just like other actions; conflicting sphere of influence declarations are resolved just like conflicting moves.
A player may not move or attack an army or fleet into a province that is currently a sphere of influence belonging to another player without first declaring war on that player.
Spheres of Influence end in two ways: either the player who has declared the sphere of influence may cancel it by writing "Undo Sphere of Influence in (Province)" or "Undo SOI in (Province)" in the orders, or an army or fleet not belonging to the player who has declared the sphere of influence may successfully move or attack into the relevant province. The player who has declared the sphere of influence loses a victory point only in the latter case.