Mercator (gp24)

by Doug Wakefield (1985 edition)


Mercator originated as an enlarged combination of the size of "Youngstown" and the mobility of "Abstraction". Played on "World" boards, many different Marks have been designed. The early ones are for 13 players and may be regarded as a series of refinements which came about as playing experience increased. This particular line ends with 'Definitive'. Subsequent Marks experiment with different combinations of extra countries.

The basic units in Mercator are - as with the Regular game - armies and fleets, but unlike in the Regular game these units may travel together for several moves, and the resulting high mobility Army/Fleets are the centrepiece of the game.

The power of the A/F comes largely from its ability to operate in different Time Scales from single units. This makes for a more tactical game, but one in which the need for diplomacy remains strong to the end, since provision is made for single, 2-way and 3-way wins. Would be outright winners have been spiked at the post by the formation of late 2 or 3 way alliances which meet the victory criteria.

The standard rules of Diplomacy apply except where modified below.


Before plunging into details I should like to express my gratitude to the many Mercator players who have contributed ideas, constructive criticism and clerical effort. These include Bob Brown, Stuart Dagger, Graham Mills, Peter Nunn, Ron Rayner, Richard Sharp and Andrew Smith. Thanks are also due to the 'Colonial' gents who provided initial inspiration - Allan Calhamer for devising the Regular game, the gentlemen of the Youngstown Diplomacy Club for coming up with the idea of a bigger board, Fred Davis for the basic idea behind the A/F's, and Jeff Key for the rule which bears his name.


The previous edition of the rules was written in 1978, and no longer covers all that needs to be covered. This edition seeks to remedy that by incorporating the clarifications which have been made over the last six years and by supplying one or two more in places where they seem to be needed.

In particular, the 'Z' movement rules have been adopted as standard, as have Andrew Smith's retreat rules and the use of the Key rule in all three Time Scales. The pressure which games players tend to put on rules had begun to cause problems over what was and was not legal in Time Scale 3, and so this section has been expanded in an attempt to make matters clearer. The only actual change to the rules has been the dropping of the one concerning the life cycle of A/F's, which has gone because in practice it never came into- play and only served to give the G.M. extra book keeping.

In the optional section the rules governing aircraft and submarines have been brought up to date.

Illustrative examples have been given where appropriate. The geography used in these is that of the Regular Diplomacy board, since this is familiar to most players. It also gets round the problem of the multiplicity of Mercator maps.

This edition of the rules has been prepared by a small committee under the chairmanship of Doug Wakefield. The other two members were Stuart Dagger and Andrew Smith.



In Regular Diplomacy armies cross water by using fleets as stepping stones; the fleets are put in position, and then over the army goes. e.g. F(ENC) & F (MAO) C A(Lon) Por.

This type of convoy is still available in Mercator, but it is not often used. Instead most convoys are effected by means of the more natural 'piggy back' rule introduced by Fred Davis in his variants such as "Abstraction". In this the army boards the fleet, which thon moves, carrying the army with it. So for the London - Portugal journey cited above the army would board the Channel fleet, the combined unit would move to MAO, and the army would land in Portugal. The second fleet is not needed. It is a more complicated rule than Calhamer's, but, as you will note, it is less cumbersome for these longer journeys. While the army and fleet stay together they are referred to as an army/fleet - A/F for short. The different time scales into which each season is split in Mercator are there partly to make it clear just when these hybrid units do what, and partly to introduce a spot of tactical mayhem. The basic pattern is

TS1   armies get on and off fleets

TS2   the usual Diplomacy moves and supports

TS3   armies get on and off fleets

So in our example the London army boards in TS1, the A/F moves to MAO in TS2, and the army disembarks in TS3. Note, however, that the army was not obliged to disembark. It could have stayed aboard and then on the next move either landed in TS1 or tried to move further in company with the fleet.


An army/fleet can only be formed by an army boarding or embarking a fleet; they can not be formed as a result of retreats, and they can not be built.

Army/fleets can only occupy sea provinces and canal provinces.

Except in the case of TSl landings the strength of an army/fleet is that of the fleet.

In TS2 an army/fleet may move to a sea or canal province.

In TS2 an army/fleet has the saure support abilities as a fleet would have in the same province. In particular, it may support another unit standing in or moving to an adjacent coastal province, even though it could not itself move to that province.


An army which is on board a fleet may land in an adjacent land province. The format for writing such orders is     A(ENC) L Lon.

The landing of an army may be supported by the carrying fleet (but only by the carrying fleet). In this case the strengths of the army and the fleet are added together, making success certain unless another supported landing is being attempted in the same province, when a stand-off results and the armies stay on board. A fleet which does support an attempted landing may do nothing further until TS3. The format for writing orders for supported landings is F(ENC) S A(ENC) L Lon. In the event of two supported landings standing each other off, a unit which began the season in the disputed province survives and may order normally in TS2 and TS3.

An army which lands in TS1 may order normally in TS2 and TS3, i.e. just as it would have done had it begun the season in the relevant province. These rights remain even if the landing is unsuccessfully opposed.

A fleet which lands an army in TS1 may order normally in TS2 and TS3 provided it did not support the landing.

An army may board a fleet in an adjacent sea or canal province. The format for writing such orders is A(Lon) B F (NTH) .

Landings and boardings take place simultaneously. A fleet may land one army and take on another - provided that it did not support the landing (when it is decreed to be to busy to do anything else).

Units dislodged as a result of TS1 landings are removed from the board until TS4 (retreats).

The Key rule applies (see rule 2.7).


The normal Diplomacy orders for armies and fleets take place, i.e. move, stand and support. Army/fleets may also move, stand and support.

TS2 orders may not be made conditional on events in TS1; it is up to the player to have anticipated what the situation will be. In particular, he or she must anticipate whether a unit is now a fleet or an army/fleet, and the order will be invalid if the player gets it wrong. For example, suppose the orders were


If the landing in TS1 fails, the subsequent move order is invalid, because the unit in ENC is not F(ENC) but A/F (ENC) .

The Key rule applies (see rule 2.7).

There are also landings from Fast Ferries and from Convoys where no .fleet moved, but for the details on these you are referred to the section on convoys.

Units dislodged in TS2 are removed from the board until TS4 (retreats).


An Army which is on board a fleet may disembark in an adjacent land province. Disembarkations may not be supported, but may be made into land provinces which are vacant as a result of a TS1 or TS2 stand-off. The format for writing such orders is A(NTH) D Hol.

An army may embark on to a fleet in an adjacent sea or canal province. The format for writing such orders is A(Spa) E F (MAO) .

Disembarkations and embarkations take place simultaneously. A fleet may disembark one army and take on another.

A fleet which has disembarked an army in TS3 or an army/fleet caused by a TS3 embarkation (whether or not preceded by a disembarkation) may attempt a further move. Such moves may only be to sea spaces and may not be supported. Fleets and army/fleets not involved in TS3 ".embarkations or disembarkations may not attempt to move in TS3.

TS3 orders may not be made conditional on events in earlier time scales. However, by the time TS3 is reached there have been quite a few 'ifs' to worry about, and it is not always clear to players whether what they want to order is legal or not. To resolve such borderline cases adopt the following guideline:- Imagine that at the start of the season each army commander is given one order of the form "if at the start of TS3 you are in province X and there is a fleet in Y then board it", and that each fleet commander is given one order of the form "if at the start of TS3 you are in sea or canal province U and there is an army in V then let it board". For the embarkation to succeed the army and fleet orders must match. If your orders admit the possibility of such instructions having been given, then they are legal; otherwise they aren't.


(a) France begins the season with F(ENC), F(MAO) and A(Gas). The only orders involving these units are

TS2 F(ENC) - NTH, F(MAO) - ENC, A(Gas) - Bre

TS3 A(Bre) E F(ENC)

The embarkation succeeds whether or not the two fleet moves are successful. Reason? Both fleet captains were ordered to pick up in the Channel.

(b) France begins the season with F(ENC), F(MAO), A(Gas), and Germany with A (Pic) . Fearing a German order A(Pic) - Bre, France orders

TS2 A(Gas) - Bre, F(ENC) - NTH, F(MAO) --ENC

TS3 A(Bre) E F(ENC), A(Gas) E F(MAO),


Both the embarkation orders are illegal, since France is taking a double option On A(Gas) - hedging his bets on the success or failure of his TS2 order.

The Key rule applies to both the embarkation/disembarkation and supplementary move phases of TS3 (see rule 2.7).


Mixed nationality army/fleets add spice to the game. Normally both players would issue identical orders, but, provided both indicate a boarding/embarkation, either may attempt to modify the 'agreed' orders to his or her advantage.

In TS1, and in the first part of TS3, the army's order takes precedence if it is compatible with the fleet's position, but if the fleet succeeds in making a move that the army has not anticipated the army order is invalidated and the fleet may land/disembark the army where it will - including the Arctic and the Antarctic (see rule 6.2). The owner of the army may not order the army/fleet in TS2 or in the second part of TS3.

As always, conditional orders are not allowed.

Some examples:


(a) German A(Bel) B F(ENC)

a/F(ENC) - NTH    A(NTH) D Nor


A(Bel) B French F(ENC)

A/f(ENC) - NTH    A(NTH) D Den


If the move to NTH succeeds and Denmark is untenanted the army lands in Denmark, otherwise it lands in Norway, or if that fails it stays on board.


(b) German A(Bel) B F(ENC)

a/F(ENC) - MAO   A (MAO) D Gas    



as (a)

as (a)


If the move to BIS succeeds the army is disembarked in Gascony; if not the result is an army/fleet in ENC.


(c) Italian A(Spa) B F(MAO)

a/F(MAO) - NAO    A (NAO) D ARC



A(Spa) B French F(MAO)

A/f(MAO) - WMS    A (WMS) D Tun


If the move to NAO succeeds the Italian army is dumped in the Arctic, where it stays for the rest of the game.

For a boarding or embarkation to succeed it must be ordered by both players. Use the format illustrated above, and remember to include the nationality of your partner's units, just as you would were you ordering support for one of his or her moves.

The use of large letters for your units and small letters for your partner's is not obligatory, but sometimes makes things clearer.

For the purposes of the rule which says that a unit can not dislodge units of the same nationality, the "nationality" of a mixed nationality army/fleet is that of the fleet.


This applies to all time scales and says that a unit which attempts to moue and is unsuccessful will be dislodged by any unsupported attack coming from any space other than that to which it was attempting to move.

The sort of situation covered is the following:

France A(Bur) - Bel

Germany A (Ruh) - Bel, A (Mun) - Bur

With the Key rule Belgium stays empty, just as it would in Regular Diplomacy, but the move to Burgundy succeeds.

It is possible for two "Key attacks" to stand each other off. For instance, if in the above example we added

Italy: A(Mar) - Bur

then the German and Italian attacks on Burgundy cancel each other out, and the French A(Bur) is not dislodged.

This example provides the pattern for application of the Key rule in TS2 and in the supplementary move section of TS3.

The sort of situation which is covered in TS1 and in the first part of TS3 is the following:‑

Germany: A(NTH) L Lon

France: A(ENC) L Lon, A (Bre) B F (ENC )

Italy: A(MAO) L Bre

Here the two attempted landings in London produce a stand-off, and the French army in Brest falls victim to the Key rule.


For your sake, and more especially for the G.M.'s, split your orders \into separate time scales - i.e. all the TS1 orders, then ail the TS2 and so on.


There are four methods of moving an army across water at Mercator.

(a) The basic "piggy back" convoy already described, in which the army boards a fleet in either TS1 or TS3, moves with it until the destination is reached and then gets off. The great majority of convoys are by this method.

(b) The Fast Ferry. This is the convoy of Regular Diplomacy, used across a single sea space. Its advantage over (a) is that the army arrives in TS2 rather than TS3. The mechanics are that the army boards the fleet in TS1 and then convoys and lands in TS2. Set out the order in the form

TS1 A(Lon) B F(ENC)

TS2 F(ENC) F/F A(Lon) - Bre

As in Regular Diplomacy the move can receive TS2 support from other units. So to the above order you might add A(Par) S A(Lon) - Bre. The order uses up the TS2 order capacity of the carrying fleet.

(c) The extended convoy of Regular Diplomacy is also available, although its use is very rare. The unit boards the first fleet in the chain in TS1. The rest of the convoy, including the landing, is in TS2. The order uses up the TS2 order capacity of all the units involved. If the landing f ails the army remains on board the last fleet in the chain. If a fleet in the chain is dislodged the army remains on board the fleet preceding the dislodged one.

e.g.  TS1 A(Den) B F(NTH) TS2 F(NTH), F(ENC) & F(MAO) C A(Den) - Por.   If F(MAO) were dislodged the result would be A/F(ENC).

(d) As (c) but the last fleet in the chain can move, taking the army with it. The army could then try to land in TS3. So 'for example the order could read

TS1 A (Den) B F (NTH)

TS2 F (NTH) & F (ENC) C A (Den) - ENC , A/F (ENC) - MAO

TS3 A (MAO) D Por

With both (c) and (d) any fleet in the chain may attempt to move off with the army, and so in international ventures of this type there is scope for creative misunderstanding.


Retreats may be thought of as taking place in time scale 4. However, this time you may make your orders conditional on what has happened ''earlier. In addition to the retreat rules of Regular Diplomacy the following conventions and restrictions apply:

(a) Units have precedence in choice of retreat space over those dislodged in later time scales

(b) Armies may not retreat on to fleets.

(c) Army/fleets may retreat intact. The army has priority of choice in retreating to land, but the fleet may delay its retreat until after the army has landed and may then move away, e.g. if A/F(MAO) is dislodged then A(MO) - Por, F(MAO) - WMS is a valid retreat order.

(d) If an army/fleet retreats intact no attempt may be made to land the army immediately. So, for example, if A/F(MAO) is dislodged you may not issue a retreat order A/F(MAO) - WMS, A(WMS) - Tun.

(e) If the fleet part of an army/fleet is disbanded, the army goes with it unless it has been expressly and previously retreated.

(f) Fleets and army/fleets dislodged by the Key rule in TS3 may only retreat to sea spaces, and in the case of army/fleets must retreat intact. This restriction does not apply in TS2.

(g) Retreats are not permitted to (1) the space from which the attacker moved (2) any space from which the attack was supported (3) any space entered by the dislodging piece in a later time scale of the same season (4) any space vacated by a foreign unit moving into the province where dislodgment occurred. (This includes a land province vacated by an army which makes an embarkation in the dislodgement sea space.)

(h) It is not possible to 'retreat' to the province that one has been dislodged from even if it is now vacant as a result of the attacker having moved on.

(i) Retreats may be made to spaces which were the scene of stand-offs in time scales other than that in which the dislodgement was made, provided that such retreats do not fall foui. of the restrictions listed under (g).


Players have greater freedom over where they can build than they do in Regular Diplomacy. Builds do not have to be taken in supply centres, and they do not have to be taken in one's home country.


Ownership of supply centres is determined as in Regular diplomacy.

The owner of a province which is neither a supply centre nor a special province is the last player to have a unit there, however fleetingly. For example, France orders

TS1 A(ENC) L Wal  TS2 A(Wal) - Lpl.

If the landing is successful France becomes the 'owner' of Wales whether or not the move to Liverpool succeeded.

Sea provinces are never owned.

Special provinces can never be owned by a person other than the one ',to whom they were initially assigned.


In many Marks each player is assigned one or two 'Special Provinces'. These are non-supply centres outside his or her home country which are not subject to the usual rules governing ownership. The assignee may build units there provided only that the province is empty. Players may not build in each other's Special Provinces.


A player may build in any owned province in his or her home country. A player may build in any of his or her Special Provinces.

A player may build in any owned province outside his or her home country by paying a 'premium'. This premium is the withholding of another build until the next adjustment period. Thus for Germany to build in an owned Gascony or Paris he or she would need an entitlement to at least two builds and would sacrifice one of them until the next build period.



Certain provinces contain important canals and are designated as "canal provinces" They have the characteristic of Kiel on the Regular map in that a unit may arrive on one 'coast' and leave on the opposite. They are also the only non-sea provinces which may be occupied by army/fleets.

In most marks the relevant canals are Suez, Panama and Kiel. The Panama canal is either in a special Panama Canal zone or in Panama, the Suez Canal either in a Suez Canal zone or in Egypt, and the Kiel Canal either in Kiel or in both Kiel and Flensburg.

On some maps Kiel (and Flensburg) are not marked as canal provinces. These should be amended by marking in 'c,p,' where appropriate.

An army/fleet in a canal province has the power of the army only. It is repeated (see 2.2) that army/fleets may not be built.


The polar caps are permanently impassable for fleets and army/fleets, but fleets may attempt to dump passenger armies into them. Any number of armies may be dumped and may never escape, be rescued or be disbanded. Thus a player who has had 3 armies dumped would play on with 3 permanent shortages.

In some of the early marks there is no sea space between the polar cap and the nearest land province. In these cases the coastal crawl by fleets along the land provinces adjoining the icecap is permitted.


On maps where they appear Sardinia is Italian and Hokkaido Japanese. In the case of islands which are home supply centres the starting positions make it clear who the owner is.


Mercator allows a little more freedom than does Regular Diplomacy in such matters as direct passage from Spain to North Africa and from the Black Sea to the Aegean. For details refer to the individual Marks.


In the event of the G.M. having to remove units he or she will follow a 'furthest from home supply centre' principle. For this purpose 'home' includes colonies (such as Cambodia for France in 'Definitive') but does not include Special Provinces. If ties have to be resolved, the tiebreakers used will be, in order,

(1) units in non-supply centres

(2) fleets which do not have armies on board

(3) armies from army/fleets

(4) fleets which no longer have armies on board

(5) armies on land

(6) alphabetical order of province abbreviation


The game year varies from Mark to Mark, but the first season is always January, the second February and so on. The build seasons are March, June, September and December of each year.


In most Marks Germany and Russia start the game with an extra unit. This unit may be either an army or a fleet, as selected by the player, and is placed in any vacant home or special province of the country concerned. The placement is made secretly by the player and is not revealed to the other players until the January moves are adjudicated.

\Units are adjusted to equal supply centre holdings at the third build season.


These vary and players should consult the individual Marks for the actual number of supply centres required in each case. In addition to single player wins provision is made for two player and three player wins. In the case of multiple player wins the two or three players concerned have to claim the win from the gamesmaster in the same season. In the event of several wins being declared in the same season a solo win has preference over a multiple player win, and a two way win over a three way win. If more than one two player (or three player) win is claimed in the same season, then the win goes to the combine having the most centres. If more than one player qualifies for a claimed solo win, the victory is shared irrespective of supply centre holding.


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