The Diplomacy gametype is a user created "custom" game with a set of rules in a FFA to be followed to play the game as a real world scenario of deceiving enemies, making valuable alliances, making "declarations" of war, and eventually being the last one standing, however, the game can be voted to end if an alliance claims "victory".
Common rules consist of:
- No attacking other players without declaring war on them in public chat so as to give the enemy a fair chance. Often both Sides have to wait a turn to attack after the war-declaration
- No attacking an player without warning (in some games this is known as "Blitzkrieging", German for "Lighting War".)
- Alliances are encouraged. Some games require alliances be made public, some allow it to be private. Allies are a good way of invading successfully or defending from a stronger enemy.
- Maximum Number of Allies a Player can have (Even if Alliances are encouraged, there's sometimes a limit so Alliances won't get too big)
Other possible rules consist of:
- Only Hosts can declare PEs
- Gangbanging forbidden/allowed (Gangbanging in this case means that many Players together attack one alone Player (Like a 5vs1). Often a Player alone can't defend himself from several Players, that's why it's often forbidden.)
- Claims (doesn't) have to be respected (Claiming means, that a Player says that a Bonus on Neutral or booted territory is his. Often Claiming doesn't need to be respected)
- Reasons for war (not) needed (Sometimes, there must be a Reason to declare War to reduce War-Mongering. An example could be that somebody didn't respected your Claim or somebody attacked your Ally.)
- Roleplay mandatory (Means, that Players actually have to Roleplay, and don't treat the Diplomacy-Game like any other Warzone-Game)
If a player breaks the custom rules of the Diplomacy Game, they aren't breaking the actual Rules of Warzone. They only become a PE for this Diplomacy-game.
 PE (Public Enemy)
Players which break Rules in a Diplomacy Games are often called a "PE", which is short for Public Enemy. In many Diplomacy Games only the Hosts can (un)declare PEs, but sometimes the Hosts also allows normal Players to (un)declare PEs.
Often all Players which are adjacent to a PE can attack the PE without warning/permission and even have to attack the PE, if they're able to. Somebody who won't attack a PE or even are helping a PE might become a PE itself.
While the exact creator is not known as after its obscure creation other users quickly copied the rules and made spinoffs, the user "Soviet Russia Buddy" takes the most credit for creating the game. His first game was known as "Reality Warfare, A New Way Of Playing", which was then shortened to "Reality Warfare" which its current name is. This can be disputed by Le Count H who was laying the foundation in scenarios in late September of 2012. These were initially unfair due their emphasis on giving nations overwhelming advantages due to their size. His games became extremely popular the following summer. Another user named "Zecit" coined the term "Public Enemy" in his game "Simulation World", which is used in many Diplomacy games. Out of all hosts commonly making these games, he (presumably male) has the most amount of rules and hosts games at least once a day. However, not all of them are rules and rather more creative and realistic additions, one of which is a rule involving capitals, and some are guidelines that can be used to be more "diplomatic". People who have played with him have said they have played that gametype with him for almost 2 years. When asked where he got his possibly original idea, he said he had been playing a 24FFA with no fog when he noticed that everyone had to have secret alliances as no one was attacking anyone.
Currently, many different players host these games. Most of them are 6FFAs, but Soviet Russia Buddy and others host 24FFAs, or sometimes less for scenario diplomacy games. While many players attribute many different users for its creation, many only use 3-4 of Soviet Russia Buddy's original rules, usually copying them word for word. Alternatively, rules are slacked and public declarations are only required if a player wants to be "trustworthy". Many diplomacy games involve a strong element of roleplay, as players play as if they were a character in whichever world the game is set in. This works especially well with maps of universes from fantasy novels, such as George RR Martin's "Song of Ice and Fire".
 Diplomacy mods
The most requested feature from Uservoice, Peace Treaties, has been implemented as a Mod. The Advanced Diplomacy Mod and Diplomacy mod remove the need for players to be "trustworthy", as declarations are not needed anymore, since if you are at peace with someone, you cannot attack each other.
Warning: As of November 2018, there are bugs with the Advanced Diplomacy mod. Use the Diplomacy mod instead
Also most Diplomacy-games are Multi-Day Games, so everyone can react easily and unstressed and because Diplomacy-Games often have many Players. But also some are Real-Time with a high Boot-Time.
Most hosts make the game a practice game.