empire -- the wargame of the century
empire [-w water] [-s smooth] [-d delay] [ -S save-interval ] [ -f
Empire is a simulation of a full-scale war between two emperors, the
computer and you. Naturally, there is only room for one, so the object
of the game is to destroy the other. The computer plays by the same
rules that you do.
-wwater This option controls the amount of water on the map. This is
given as the percentage of the map which should be water.
The default is 70% water. water must be an integer in the
between 10 and 90 inclusive.
-ssmooth This controls the smoothness of the map. A low value will
produce a highly chaotic map with lots of small islands or
lakes. A high value will produce a map with a few scattered
continents. Be forewarned that a high value will cause the
program to take a long time to start up. The default value
-ddelay This option controls the length of time the computer will
delay after printing informational messages at the top of the
screen. delay is specified in milliseconds. The default
value is 2000 which allows the user two seconds to read a
empire -w90 -s2
This produces a map with many islands.
empire -w50 -s0
This produces a really strange map. These values are not recommended
for the faint at heart.
This produces a map with lots of land and a few lakes. The computer
will have a hard time on this sort of map as it will try and produce
lots of troop transports, which are fairly useless.
There are two other option.
sets the save interval for the game (default is 10). Once per
interval turns the game state will be automatically saved after
your move. It will be saved in any case when you change modes or
do various special things from command mode, such as ‘M’ or ‘N’.
Set the save file name (normally empsave.dat).
Empire is a war game played between you and the user. The world on
which the game takes place is a square rectangle containing cities,
land, and water. Cities are used to build armies, planes, and ships
which can move across the world destroying enemy pieces, exploring, and
capturing more cities. The objective of the game is to destroy all the
enemy pieces, and capture all the cities.
The world is a rectangle 60 by 100 squares on a side. The world
consists of sea (.), land (+), uncontrolled cities (*), computer-
controlled cities (X), and cities that you control (O).
The world is displayed on the player’s screen during movement. (On
terminals with small screens, only a portion of the world is shown at
any one time.) Each piece is represented by a unique character on the
map. With a few exceptions, you can only have one piece on a given
location. On the map, you are shown only the 8 squares adjacent to
your units. This information is updated before and during each of your
moves. The map displays the most recent information known.
The game starts by assigning you one city and the computer one city.
Cities can produce new pieces. Every city that you own produces more
pieces for you according to the cost of the desired piece. The typical
play of the game is to issue the Automove command until you decide to
do something special. During movement in each round, the player is
prompted to move each piece that does not otherwise have an assigned
Map coordinates are 4-digit numbers. The first two digits are the row,
the second two digits are the column.
The pieces are as follows:
|Piece | You | Enemy | Moves | Hits | Str | Cost |
|Army | A | a | 1 | 1 | 1 | 5(6) |
|Fighter | F | f | 8 | 1 | 1 | 10(12) |
|Patrol Boat | P | p | 4 | 1 | 1 | 15(18) |
|Destroyer | D | d | 2 | 3 | 1 | 20(24) |
|Submarine | S | s | 2 | 2 | 3 | 20(24) |
|Troop Transport | T | t | 2 | 1 | 1 | 30(36) |
|Aircraft Carrier | C | c | 2 | 8 | 1 | 30(36) |
|Battleship | B | b | 2 | 10 | 2 | 40(48) |
|Satellite | Z | z | 10 | -- | -- | 50(60) |
The second column shows the map representation for your units.
The third shows the representations of enemy units.
Moves is the number of squares that the unit can move in a single
Hits is the amount of damage a unit can take before it is destroyed.
Strength is the amount of damage a unit can inflict upon an enemy
during each round of an attack.
Cost is the number of rounds needed for a city to produce the piece.
The number in parenthesis is the cost for a city to produce the first
Each piece has certain advantages associated with it that can make it
useful. One of the primary strategic aspects of this game is deciding
which pieces will be produced and in what quantities.
Armies can only move on land, and are the only piece that can move on
land. Only armies can capture cities. This means that you must
produce armies in order to win the game. Armies have a 50% chance of
capturing a city when they attack. (Attacking one’s own city results
in the army’s destruction. Armies that move onto the sea will drown.
Armies can attack objects at sea, but even if they win, they will
drown.) Armies can be carried by troop transports. If an army is
moved onto a troop transport, then whenever the transport is moved, the
army will be moved with the transport. You cannot attack any piece at
sea while on a transport.
Fighters move over both land and sea, and they move 8 squares per
round. Their high speed and great mobility make fighters ideal for
exploring. However, fighters must periodically land at user-owned
cities for refueling. A fighter can travel 32 squares without
refeuling. Fighters are also shot down if they attempt to fly over a
city which is not owned by the user.
Patrol boats are fast but lightly armored. Therefore they are useful
for patrolling ocean waters and exploring. In an attack against a
stronger boat, however, patrol boats will suffer heavy casulties.
Destroyers are fairly heavily armored and reasonably quick to produce.
Thus they are useful for destroying enemy transports which may be
trying to spread the enemy across the face of the world.
When a submarine scores a hit, 3 hits are exacted instead of 1. Thus
submarines can inflict heavy damage in a fight against heavily armored
boats. Notice that healthy submarines will typically defeat healthy
destroyers two-thirds of the time. However, a submarine will defeat a
fighter about two-thirds of the time, while a destroyer will defeat a
fighter three-fourths of the time.
Troop transports are the only pieces that can carry armies. A maximum
of six armies can be carried by a transport. On any world containing a
reasonable amount of water, transports will be a critical resource in
winning the game. Notice that the weakness of transports implies they
need protection from stronger ships.
Aircraft carriers are the only ships that can carry fighters. Carriers
carry a maximum of the number of hits left of fighters. Fighters are
refueled when they land on a carrier.
Battleships are similar to destroyers except that they are much
Satellites are only useful for reconaissance. They can not be
attacked. They are launched in a random diagonal orbit, and stay up
for 50 turns. They can see one square farther than other objects.
All ships can move only on sea. Ships can also dock in a user-owned
city. Docked ships have damage repaired at the rate of 1 hit per turn.
Ships which have suffered a lot of damage will move more slowly.
Because of their ability to be repaired, ships with lots of hits such
as Carriers and Battleships have an additional advantage. After
suffering minor damage while destroying enemy shipping, these ships can
sail back to port and be quickly repaired before the enemy has time to
replenish her destroyed shipping.
The following table gives the probability that the piece listed on the
side will defeat the piece listed at the top in a battle. (The table
assumes that both pieces are undamaged.)
|vs. | AFPT | D | S | C | B |
|AFPT | 50.0% | 12.5% | 25.0% | 00.391% | 00.0977% |
|D | 87.5% | 50.0% | 25.0% | 05.47% | 00.537% |
|S | 75.0% | 75.0% | 50.0% | 31.3% | 06.25% |
|C | 99.6% | 94.5% | 68.7% | 50.0% | 04.61% |
|B | 99.9% | 99.5% | 93.8% | 95.4% | 50.0% |
Notice, however, that when a ship has been damaged, the odds of being
defeated can go up quite a bit. For example, a healthy submarine has a
25% chance of defeating a battleship that has had one hit of damage
done to it, and a healthy submarine has a 50% chance of defeating a
carrier which has suffered two hits of damage.
There are a variety of movement functions. The movement functions of
pieces can be specified in user mode and edit mode. Cities can have
movement functions set for each type of piece. When a movement
function for a type of pieces is set for a city, then every time that
type of piece appears in the city, the piece will acquire that movement
function. Be forewarned that moving loaded transports or loaded
carriers into a city can have undesirable side effects.
Normally, when a movement function has been specified, the piece will
continue moving according to that function until one of the following
* An enemy piece or unowned city appears next to the piece. In this
case the piece will be completely awoken, unless its movement
function has been set to a specific destination. Armies on ships
and pieces inside cities will not be awoken if the enemy piece is
gone by the time it is their turn to move.
* You explicitly awaken the piece.
* The piece can no longer move in accordance with its programmed
function. In this case, the piece will awaken temporarily. You
will be asked to move the piece at which time you may awaken it.
* The piece is a fighter which has just enough fuel (plus a small
reserve) to get to the nearest city. In this case, the piece will
awaken completely, unless its movement function has been set to a
specific destination, or its movement function has been set to
The rationale behind this complexity is that fighters must be awoken
completely before they are out of range of a city to prevent one from
accidentally forgetting to waken the fighter and then watching it fly
off to its doom. However, it is presumed that when a path is set for
the fighter, the fighter is not in danger of running out of fuel.
Pieces do not completely awaken when their function has been set to a
destination because it is slightly time consuming to reset the
destination, but very simple (one keystroke) to wake the piece.
The movement functions are:
Attack This function applies only to armies. When this function is
set, the army will move toward the nearest enemy city,
unowned city, or enemy army. This is useful when fighting
off an invading enemy or taking over a new continent. When
an army is set to this mode, it will also explore nearby
territory. This tends to make the "grope" movement mode
Awake When pieces are awake, you will be asked for the direction in
which the piece should move on each turn.
Fill This function applies to carriers and transports. When this
function is specified, these ships sleep until they have been
filled with fighters or armies respectively.
Grope This function causes a piece to explore. The piece heads
toward the nearest unseen square of the map on each of its
moves. Some attempt is made to explore in an optimal
Land This function applies to fighters and causes the fighter to
head toward the nearest transport or carrier.
Random This movement function causes a piece to move at random to an
adjacent empty square.
Sentry This movement function puts a piece to sleep. The function
of a city cannot be set to ’sleep’.
Transport This movement function only works on armies. The army sleeps
until an unfull transport passes by, at which point the army
wakes up and boards the transport.
Upgrade This movement function only works with ships. The ship will
move to the nearest owned city and remain there until it is
<dir> Pieces can be set to move in a specified direction.
<dest> Pieces can be set to move toward a specified square. In this
movement mode, pieces take a shortest path toward the
destination. Pieces moving in accordance with this function
prefer diagonal moves that explore territory. Because of
this, the movement of the piece may be non-intuitive.
As examples of how to use these movement functions, typically when I
have a new city on a continent, I set the Army function of the city to
attack. Whenever an army is produced, it merrily goes off on its way
exploring the continent and moving towards unowned cities or enemy
armies or cities.
I frequently set the ship functions for cities that are far from the
front to automatically move ships towards the front.
When I have armies on a continent, but there is nothing to explore or
attack, I move the army to the shore and use the transport function to
have that army hop aboard the first passing transport.
There are three command modes. The first of these is "command mode".
In this mode, you give commands that affect the game as a whole. In
the second mode, "move mode", you give commands to move your pieces.
The third mode is "edit mode", and in this mode you can edit the
functions of your pieces and examine various portions of the map.
All commands are one character long. The full mnemonic names are
listed below as a memorization aid. The mnemonics are somewhat
contrived because there are so few characters in the English language.
Too bad this program isn’t written in Japanese, neh?
In all command modes, typing "H" will print out a screen of help
information, and typing <ctrl-L> will redraw the screen.
In command mode, the computer will prompt you for your orders. The
following commands can be given at this time:
Automove Enter automove mode. This command begins a new round of
movement. You will remain in move mode after each of the
computer’s turns. (In move mode, the "O" command will return
you to command mode after the computer finishes its next
City Give the computer a random unowned city. This command is
useful if you find that the computer is getting too easy to
Date The current round is displayed.
Examine Examine the enemy’s map. This command is only valid after
the computer has resigned.
File Print a copy of the map to the specified file.
Give This command gives the computer a free move.
J Enter edit mode where you can examine and change the
functions associated with your pieces and cities.
Move Enter move mode for a single round.
N Give the computer the number of free moves you specify.
Print Display a sector on the screen.
Quit Quit the game.
Restore Restore the game from empsave.dat.
Save Save the game in empsave.dat.
Trace This command toggles a flag. When the flag is set, after
each move, either yours or the computer’s, a picture of the
world is written out to the file ’empmovie.dat’. Watch out!
This command produces lots of output.
Watch This command allows you to watch a saved movie. The movie is
displayed in a condensed version so that it will fit on a
single screen, so the output may be a little confusing. This
command is only legal if the computer resigns. If you lose
the game, you cannot replay a movie to learn the secrets of
how the computer beat you. Nor can you replay a movie to
find out the current positions of the computer’s pieces.
When replaying a movie, it is recommended that you use the -d
option to set the delay to around 2000 milliseconds or so.
Otherwise the screen will be updated too quickly for you to
really grasp what is going on.
Zoom Display a condensed version of the map on the screen. The
user map is divided into small rectangles. Each rectangle is
displayed as one square on the screen. If there is a city in
a rectangle, then it is displayed. Otherwise enemy pieces
are displayed, then user pieces, then land, then water, and
then unexplored territory. When pieces are displayed, ships
are preferred to fighters and armies.
In move mode, the cursor will appear on the screen at the position of
each piece that needs to be moved. You can then give commands to move
the piece. Directions to move are specified by the following keys:
These keys move in the direction of the key from S. The characters are
not echoed and only 1 character is accepted, so there is no need for a
<Return>. Hit the <Space> bar if you want the piece to stay put.
Other commands are:
Build Change the production of a city.
Fill Set the function of a troop transport or aircraft carrier to
Grope Set the function of a piece to grope.
Idir Set the direction for a piece to move.
J Enter edit mode.
Kill Wake up the piece. If the piece is a transport or carrier,
pieces on board will not be awoken.
Land Set a fighter’s function to land.
Out Cancel automove mode. At the end of the round, you will be
placed in command mode.
Print Redraw the screen.
Random Set a piece’s function to random.
Sentry Set a piece’s function to sentry.
Transport Set an army’s function to transport.
Upgrade Set a ship’s function to upgrade.
Set the city movement function for the specified piece to the
specified function. For example, typing "VAY" would set the
city movement function for armies to attack. Whenever an
army is produced in the city (or whenever a loaded transport
enters the city), the army’s movement function would be set
Y Set an army’s function to attack.
? Display information about the piece. The function, hits
left, range, and number of items on board are displayed.
Attacking something is accomplished by moving onto the square of the
unit you wish to attack. Hits are traded off at 50% probability of a
hit landing on one or the other units until one unit is totally
destroyed. There is only 1 possible winner.
You are "allowed" to do fatal things like attack your own cities or
other pieces. If you try to make a fatal move, the computer will warn
you and give you a chance to change your mind.
You cannot move onto the edge of the world.
In edit mode, you can move around the world and examine pieces or
assign them new functions. To move the cursor around, use the standard
direction keys. Other commands are:
Build Change the production of the city under the cursor. The
program will prompt for the new production, and you should
respond with the key corresponding to the letter of the piece
that you want produced.
Fill Set a transport’s or carrier’s function to fill.
Grope Set a piece’s function to grope.
Idir Set the function of a piece (or city) to the specified
Kill Wake all pieces at the current location. If the location is
a city, the fighter path will also be canceled.
Mark Select the piece or city at the current location. This
command is used with the "N" command.
N Set the destination of the piece previously selected with the
"M" command to the current square.
Out Exit edit mode.
Display a new sector of the map. The map is divided into ten
sectors of size 20 by 70. Sector zero is in the upper-left
corner of the map. Sector four is in the lower-left corner
of the map. Sector five is in the upper-right corner, and
sector nine is in the lower-right corner.
Random Set a piece to move randomly.
Sentry Put a piece to sleep.
Transport Set an army’s function to transport.
Upgrade Set a ship’s function to upgrade.
Set the city movement function for a piece.
Y Set an army’s function to attack.
? Display information about a piece or city. For a city, the
production, time of completion of the next piece, movement
functions, and the number of fighters and ships in the city
Note that you cannot directly affect anything inside a city with the
After you have played this game for a while, you will probably find
that the computer is immensely easy to beat. Here are some ideas you
can try that may make the game more interesting.
* Give the computer one or more extra cities before starting the
* Try playing the game with a low smoothness value (try using the
-s2 or even -s0 option).
* When starting the game, the program will ask you what difficulty
level you want. Here "difficulty level" is a misnomer. To
compute a difficulty level, the program looks at each continent
and counts the number of cities on the continents. A high
"difficulty level" gives the computer a large continent with many
cities, while the user gets a small continent with few cities. A
low "difficulty level" has the opposite effect. It may be the
case that the computer will play better when the "difficulty
level" is low. The reason for this is that the computer is forced
to move armies to multiple continents early in the game.
Apparently, this game was originally written outside of Digital,
probably at a university. The game was ported to DEC’s VAX/VMS from
the TOPS-10/20 FORTRAN sources available around fall 1979. The
original authors listed in my old documentation are Mario DeNobili and
Thomas N. Paulson. Support for different terminal types was added by
Ed James got hold of the sources at Berkeley and converted portions of
the code to C, mostly to use curses for the screen handling. He
published his modified sources on the net in December 1986. Because
this game ran on VMS machines for so long, a previous version is known
as VMS Empire.
In 1987 Chuck Simmons at Amdahl reverse engineered the program and
wrote a version completely written in C. In doing so, he completely
modified the computer strategy, the commands, the piece types, many of
the piece attributes, and the algorithm for creating maps.
holds a backup of the game. Whenever empire is run, it will
reload any game in this file.
holds a history of the game so that the game can be replayed
as a "movie".
No doubt numerous.
Satellites are not completely implemented. You should be able to move
to a square that contains a satellite, but the program won’t let you.
Enemy satellites should not cause your pieces to awaken.
Original concept by Mario DeNobili and Thomas N. Paulson.
Support for different terminal types added by Craig Leres.
Curses support added by Ed James.
C/Unix version written by Chuck Simmons
Colorization by Eric S. Raymond.
Probability table corrected by Michael Self.
Copyright (C) 1987, 1988 Chuck Simmons
See the file COPYING, distributed with empire, for restriction and