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Basic rules

Initial setup

Seven nations comprise the European landscape of Diplomacy: Austria-Hungary, England, France, Germany, Italy, Russia, and Turkey.  Each nation starts with three military units (Army or Fleet), except for Russia who gets four (two of each type).  Additionally, each nation starts with two Army units, and one Fleet unit, except for England, and in our case, Italy as well, both of whom get two Fleets and one Army.  See the following table for starting unit distribution.

CountryArmy icon Armies in...Fleet icon Fleets in...Total Army icon / Fleet icon
Austria-Hungary Vienna,  Budapest Trieste 2/1
England Liverpool Edinburgh,  London 1/2
France Paris,  Marseilles Brest 2/1
Germany Berlin,  Munich Kiel 2/1
Italy Venice Naples,  Rome* 1/2
Russia Moscow,  Warsaw Sevastopol,  St. Petersburg (SC)** 2/2
Turkey Constantinople,  Smyrna Ankara 2/1
*Italy may start with either a Fleet or Army in Rome.  Army is traditional, Fleet is recommended.
**(SC) = South Coast; Some areas have 2 unique coastlines that affect how Fleets move, see issuing orders

Supply centers

The number of military units that each nation gets is not arbitrary.  In fact, it is dictated by a very important game mechanic called supply centers.  Looking back to the map, you'll notice that some of the geographic areas have a little star inside them.  These are the supply centers.  You get one Army or Fleet for every supply center you control.  There are a total of 34 supply centers on the map, only 12 of which are not controlled when the game starts.  In order to gain control of a supply center, you must have a unit on that land tile at the end of the Fall turn (see standard round).  Once you control a supply center, it is yours until an opponent takes it away from you.  You do not have to keep a unit stationed there to maintain control.

Winning and losing the game

In order to win the game, a player must control 18 (one more than half) of the total supply centers on the map.  Contrastingly, a player has lost the game if he or she no longer controls any supply centers at the end of a Fall turn (see standard round).  However, things are not as simple as they might seem...


Standard round

In the setting of the game, play begins at the turn of the 20th century.  In keeping with the more primitive time, things happened at a more protracted rate.  As such, there are only two rounds to each "year", a Spring round and a Fall round.  Please refer to the following chart for a diagram of the turn phases.

One year
Spring round
Negotiations
Movement orders
Conflict resolution
Retreat orders


Fall round
Negotiations
Movement orders
Conflict resolution
Retreat orders
Count supply centers
Adjust unit total

Negotiations
During this phase, the players communicate with one another to discuss, coordinate and otherwise plan their next set of move orders.
Movement orders
Here, the players separate, write down, and send in their move orders before the deadline.  (See issuing orders.)
Conflict resolution
This is the time when all of the movement orders are revealed and resolved according to the rules stated below.
Retreat orders
If your unit has become dislodged by an opposing force (see resolving conflicts), then you must move the affected unit to an adjacent, empty tile or disband (destroy) the unit.  If there are no empty tiles adjacent, the unit must be disbanded.  You may not retreat into the location the attack originated from, as the attacking unit doesn't officially move out of its location until your unit has retreated.  Similarly, you may not retreat to a tile that had a "bounce" occur this turn, even if it remains empty.
Count supply centers
Count the number of supply centers you have, adding one for each supply center owned by an opponent that your troops occupy at the end of the Fall round.  (They lose control, and you gain it.)
Adjust unit total
See building troops.

Issuing orders

For as complicated as negotiating your way to victory can be, the unit commands in Diplomacy are quite simple.  Because only one unit may occupy any area tile at any time, it is crucial to have a good understanding of each command.  However, there are only four commands that you must master:

Hold
Army Constantinople HOLD
This is the default action for every unit if no other is specified, or if an order is inappropriately given (i.e. ordering an Army to move to a water tile).  It simply means that you want the indicated unit to remain where it is.
Move/Attack
Army Paris → Picardy
Issues a command for the selected unit to move from its present location to an adjacent one.  There are some obvious limitations to this command.  An Army unit cannot move onto a sea tile at any time.  A Fleet can only move onto a land tile if part of it touches a sea tile.  Some areas do not have a continuous coastline, or touch different bodies of water on different sides.  To account for this, there are three areas with two coastlines: Spain, St. Petersburg, and Bulgaria.  Fleets treat these different coasts as if they were not adjacent territories.  That is to say that a Fleet cannot move from one such coast to an area that is only touched by the other coast.  Furthermore, a Fleet cannot move from one coast to the other, as this would require them to move over land.  Units may not swap locations (e.g. Unit A → B, Unit B → A = Unit A HOLD, Unit B HOLD).  This is because armies cannot move through each other and/or do not move at exactly the same time.  Finally, Kiel, Denmark and Constantinople may be traversed through by either a Fleet or an Army.
Support
Army Silesia SUPPORT Army Prussia → Warsaw;  Fleet Baltic Sea SUPPORT Army Berlin HOLD
This is the most important order in the game, and probably the easiest to misunderstand.  Support is what is used to determine who wins and who is forced to retreat when two units collide.  This will be explained more thoroughly in the resolving conflicts section, but basically, when two units try to move into the same area, the one with more support behind it succeeds, while the other fails (termed bouncing).  Unit A can support Unit B only if Unit A could have legally issued a move order into Unit B's tile.  A unit can never support itself.  A unit can support an opponent's unit.  Any order can be supported, and support counts as a HOLD for the unit issuing the SUPPORT.
Convoy  (Fleet only)
Army Yorkshire → Norway, Fleet North Sea CONVOY Army Yorkshire → Norway
The Fleet convoy can be a tricky command to execute, but it can sometimes be vital (like for England to leave her little island).  There are two steps needed for a CONVOY to be successful.  One, an Army must issue a MOVE order.  Seems obvious, but it's important to note that the CONVOY order itself (from the Fleet) is insufficient to actually convoy the army (this would allow people to CONVOY armies against their will).  The second step requires a Fleet to be adjacent to both the Army and the destination tile.  The CONVOY order counts as a HOLD for the Fleet itself.  A Fleet in a costal tile may not convoy.  You can chain together a long series of fleets to move a single army a very long way in one turn.  In this case, each Fleet's order would be to convoy to the location of the next Fleet, while the Army's order would still be just to move from present to final location.  You may choose to support the Fleet performing the convoy, or the Army moving into the destination tile, if you wish.  You can choose to convoy, or be convoyed by, an opponent.  Should the convoy fail for whatever reason, the Army remains in its original tile.


Resolving conflicts

Here's where all the action goes down.  After all of the orders have been sent in (or the deadline has elapsed), the results are determined.  Here's a quick guide to understanding how this process occurs:

  1. The first step is interpreting orders.  Orders must be written in a fairly rigid fashion with very little margin for error, partly out of tradition and partly to remove confusion.  Orders that are improperly given, such as ordering an Army to a sea tile, are automatically discarded and replaced with a HOLD for the units in question.
    • Discarded orders — Orders cannot be taken into effect if they are given invalidly.

      1. Austria-Hungary Army Vienna → Tyrolia
        Fleet Trieste SUPPORT Army Vienna → Tyrolia                 Result Army Vienna → Tyrolia
        Fleet Trieste HOLD         Fleet Trieste holds because it cannot support a tile it cannot move to itself.
  2. The next step is to move uncontested units.  For example, Army Trieste → Serbia succeeds if no other units attempt to move into Serbia and no unit currently resides in Serbia.
  3. Finally, conflict resolution, or if you prefer, combat.  In Diplomacy!, all military units are considered to have exactly equal combat potency.  As such, offensive action is resolved by amount of support (see Issuing orders : Support).
    • Equal support — This situation is often referred to as a bounce;  neither unit has more force than the other, so both return (or rebound) to their original positions.

      1. England Fleet North Sea → Belgium France Army Picardy → Belgium Germany Army Belgium HOLD Result Fleet North Sea HOLD
        Army Picardy HOLD
        Army Belgium HOLD         Any two orders on the left produce these results.

      2. England Army Yorkshire → Norway
        Fleet North Sea CONVOY Army Yorkshire → Norway         France Fleet English Channel → North Sea Germany Fleet Denmark → North Sea         Result Army York convoys to Norway
        Fleet English Channel HOLD
        Fleet Denmark HOLD         Because one Fleet did not SUPPORT the other's MOVE into North Sea, the CONVOY was successful.  Alternatively, had Fleet Denmark tried to move into Norway, the convoy would have bounced.
    • Unequal support — Here's where the fun happens.  For the side that has greater support, their orders are carried out to the letter.
      For the side that has lesser support, however, things vary depending on context...
      1. Supported move
        Austria-Hungary Army Galicia → Rumania
        Army Budapest SUPPORT Army Galicia → Rumania         Russia Army Ukraine → Rumania         Result Army Galicia moves into Rumania.
        Armies Budapest and Ukraine HOLD.
      2. Dislodge
        Italy Fleet Ionian Sea → Greece
        Army Albania SUPPORT Fleet Ionian Sea → Greece         Turkey Army Greece HOLD         Result Army Greece (dislodged) must retreat or disband.
        Fleet Ionian Sea moves into Greece.
      3. Cutting support – If you attack a unit that is currently lending SUPPORT, the unit attacked automatically converts to a HOLD order, to defend against the offensive, and the previously supported unit no longer receives this benefit.
        Russia Army Warsaw HOLD Germany Army Prussia → Warsaw
        Army Silesia SUPPORT Army Prussia → Warsaw         Austria-Hungary Army Bohemia → Silesia         Result Army Bohemia cuts support of Army Silesia.
        Armies Prussia and Bohemia bounce.
        Army Warsaw HOLD         Had Prussia and Silesia swapped roles, all Army Bohemia would do is move in to the recently vacated Silesa, after Army Silesia moved to Warsaw, which would've been dislodged.
      4. A unit may not, however, cut the support of another unit that is attacking it.
        Germany Army Prussia → Warsaw
        Army Silesia SUPPORT Army Prussia → Warsaw         Russia Army Warsaw → Silesia         Result Army Warsaw is dislodged.
        Army Prussia moves into Silesia.         Warsaw cannot cut the support of the unit attacking it.

Another important note, you cannot perform an action of "friendly fire", which is to say dislodge or cut the support of one of your own units.


Building troops

The supply centers you start with are special because they are the only ones you can build on and are referred to as home supply centers.  Capturing the home supply centers of another nation does not permit you to build from there.  Building is conducted in the "Winter round" (end of the Fall round and before the Spring).  The only restriction to building, aside from having to build at your own home supply centers, is that you cannot build a Fleet in a tile that is landlocked.  Because there are only three home supply centers per nationality, you can never build more than three units at a time.  This almost goes without saying, but you cannot build in a home supply center if one of your own units already occupies that tile.

On the contrary, if you have a lesser number of supply centers this build phase than you did last time, you must select units to disband (you may choose any of your troops) until you have equalled the number of supply centers that remain under your control.

Note: Losing all of your home supply centers does not mean you lose the game, simply that you cannot build until you have reclaimed them.

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