Master of Orion

Master of Orion (MoO or MOO) is a turn-based, 4X science fiction computer strategy game released in 1993 by MicroProse on the MS-DOS and Mac OS operating systems. The purpose of the game is to lead one of ten races to dominate the galaxy through a combination of diplomacy and conquest while developing technology, exploring and colonizing star systems. The game uses a point-and-click interface as well as keyboard shortcuts to control the management of colonies, technology, ship construction, diplomacy and combat. The name is a reference to the Orion system, the conquerable homeworld of a mythical race that once controlled the galaxy.

Two sequels were created, (Master of Orion II: Battle at Antares in 1996 and Master of Orion III in 2003) as well as the open source freeware FreeOrion which is loosely based on the series. A prototype was developed under the name Star Lords though it was only released as freeware in 2001 as part of the promotion for MoO III.

Master of Orion was well received, and is a member of GameSpy's Hall of Fame and GameSpot Greatest Games of All Time.


Master of Orion is a significantly expanded and refined version of the prototype/prequel program Star Lords. Steve Barcia's game development company Simtex demonstrated Star Lords to MicroProse and gaming journalist Alan Emrich who, along with Tom Hughes, assisted Barcia in refining the design to produce Master of Orion; in fact the game's manual thanks them for their contributions. Emrich and Hughes later wrote the strategy guide for the finished product. MicroProse published the final version of the game in 1993. Emrich coined the term "4X game" (eXplore, eXpand, eXploit, eXterminate) to describe the game in a preview, though Master of Orion was not the first in this genre - Civilization was published in 1991 and Reach for the Stars in the early 1980s.


Master of Orion was very well received upon its release, and is a member of both GameSpy's Hall of Fame and GameSpot's list of the Greatest Games of All Time.

System environment

Master of Orion does not offer a multi-player mode, only contests against AI opponents on the user's computer.

The game runs under MS-DOS or Mac OS. The MS-DOS version uses memory management techniques which are incompatible with Windows 95, Windows NT and their descendants including Windows XP and Windows Vista. The program can be run on these operating systems by altering some software configuration parameters to create a customized MS-DOS environment, but this presents some risks if done incorrectly. The game can also be run via the DOSBox emulator, which runs as a Windows application, avoiding the need to customize operating system parameters and allowing the use of normal Windows facilities such as ALT-TAB task switching. DOSBox uses significant amounts of RAM and CPU power to emulate MS-DOS and may be rather slow on older computers (built much before 2004). Linux users can also use DOSBox to run MS-DOS programs.

The game was distributed on 4 floppy disks and uses a 320x200 pixel, 256 color screen; sound is limited to weapons effects and a small number of MIDI tunes.


Master of Orion is a turn-based game in which players alternate actions and decisions with computer-controlled opponents. Control is primarily point-and-click; the original version was exclusively mouse-drive but a patch later allowed the use of hot keys to access many functions.

The main screen is a scrollable map of the galaxy; clicking on a system makes the rightmost part of the main screen displays information about the planet there: if the player has a colony there, controls to allocate its output; if another empire owns it, its current and maximum population; if the player has not explored the system, the word "unexplored" appears. Buttons lining the bottom of the screen access controls for other aspects of the game.

There is a separate space combat map, and additional screens for managing research, diplomacy and espionage. The diplomacy and espionage screen acts partly as a menu that provides access to screens about specific aspects. There is also a Planets List screen that can be used in managing an empire's economy.

Lockable sliders are used to allocate a colony's output between ship construction, planetary defenses, factory construction, ecology or research. The technology screen uses a similar set of lockable sliders to allocate research spending between the 6 technology areas.


The loremasters call it Orion and it is written in legend that he who masters Orion masters the universe.
The game begins with a single colonized home world and two scout ships that can be used to explore nearby stars. As the game progresses, new worlds are discovered, other races encountered, worlds colonized and wars fought. Despite their different backgrounds and homeworlds, all races possess legends of the Orions, a master race that once controlled the galaxy, and their protected homeworld containing powerful secrets and technology. The homeworld is found in the Orion star system and is defended by a powerful robotic starship, the Guardian.

Victory conditions

Victory is gained either by eliminating all opponents or by being elected supreme leader of the galaxy at a meeting of the High Council. Elections are held every 25 turns after two-thirds of the planets in the galaxy have been colonized, and each empire's voting strength depends on its population. To be elected High Master, an empire's leader must gain at least two-thirds of all available votes, with abstentions counting as a vote against both candidates. Some combination of conquest and diplomacy is necessary in order to gain such a large majority. Once a High Master is elected the other races can accept the result or challenge it; the latter results in a "Final War" that is fought to the death between the High Master's supporters and the dissidents.

Despite the game's name, conquering the Orion star system is neither necessary nor sufficient on its own to win the game. The planet in the Orion system is unusually large and extremely valuable, since artifacts left by its former inhabitants give its conqueror some very advanced military technologies, one of which players cannot research for themselves, and a colony there will be four times more productive in research than on most other planets. Other races are also more likely to support the empire that holds Orion during High Council elections. In order to colonize Orion or capture its technology one must destroy the Guardian, a far more powerful warship than any that players can build.


All of a colony's outputs are based on its industrial production, including research. All citizens are capable of industrial production, but are significantly more productive when assisted by factories. There is a limit on the number of factories a unit of population (notionally 1M individuals) can operate, but players can increase this by researching and building upgrades. The cost of upgrades rises rapidly unless the player first researches technologies that reduce factory costs.

Players can allocate a planet's industrial output for several purposes - building or upgrading factories, building or upgrading a planet's shields and missile bases, research, spaceship construction and ecology (pollution control, terraforming, increasing population growth). A planet's output can also be directed (with a 50% penalty) to the planetary reserve (treasury), which can be used to boost the output of other planets.

Production also creates pollution, which must be cleaned up by diverting resources from other purposes and acts as a serious constraint on economic growth in the early game. Various technologies reduce the cost of clean up to the point that pollution may not be a significant factor in later stages. Players must also pay maintenance costs for ships, missile bases and spies, which is a percentage tax that is applied to production at all colonies; players cannot control how this burden is allocated between colonies.


The software generates a map randomly at the start of each game; the player's only influence over the map generator is the ability to choose the size of the galaxy and the number of AI opponents. Star systems have at most one colonizable planet and a few have none. Planets vary by size, type, habitability, mineral wealth and the presence of artifacts:
Mineral wealth Productivity in factory, defense and ship construction
Ultra-poor 33%
Poor 50%
Normal 100%
Rich 200%
Ultra-rich 300%

  • Mineral wealth dramatically influences a colony's industrial productivity when building or upgrading factories, building or upgrading defenses and building ships; mineral wealth has no impact on the productivity of research nor of ecological improvements (pollution control, terraforming, etc.).
  • Size, which determines the planet's initial population capacity. This can be more than doubled by various kinds of terraforming.
  • Habitability influences population growth rates: fertile planets increase growth rates by 50% and Gaia planets by 100%, while hostile planets halve them. There are seven "normal" and six hostile planet types; the hostile types require increasingly advanced technology to colonize, which extends the exploration and colonization phases of MoO for much longer than in most 4X games. All planets can be upgraded to Gaia class with the appropriate technologies.
  • Artifact worlds contain relics of a now-vanished advanced civilization. These usually provide a free technology advance to the first empire that discovers the planet, and double the research productivity of a colony there. On Orion the conquering race receives four technology advances and the research productivity of a colony there is quadrupled.


Technology can be acquired through research, trading, spying or conquest. There are six technology areas that can be researched to produce new advances:

  1. Computers: spaceship systems that improve combat effectiveness; factory controls that increase the number of factories each colonist can operate; scanners that monitor the movements of other empires' ships and eventually can even "explore" planets remotely; and a weapon that can destroy other ships' computer systems. Computer technology advances also improve the effectiveness of spies in both offensive and defensive operations.
  2. Construction: reductions in the cost of building and upgrading factories; reductions in pollution; improved spaceship armor; and self-repair systems for ships.
  3. Force fields: protective shields for ships, planets and ground troops; devices that make it harder to hit the players' ships; and some special weapons.
  4. Planetology: reductions in the cost of pollution control; colonization of hostile planets; terraforming, which increases the maximum population of a planet; the ability to increase populations more efficiently; biological weapons and defenses against such weapons.
  5. Propulsion: increases in the range and speed of starships; some special weapons and combat systems. Range increases are particularly important in the beginning of the game
  6. Weapons for use by ships, missile bases and ground troops.

If a ship uses a component from a particular technology area, further advances in that area reduce the cost and size of the component; this effect is called "miniaturization". When one has researched all of the technologies in an area of the tech tree, further research can discover "advanced technologies" in that area, which do not provide specific new capabilities but increase the miniaturization of ship components.

Players can research several technologies at the same time, controlling the allocation of research resources by means of lockable sliders on the Technology screen. One will generally obtain more advances for a given expenditure by researching a few technologies at the same time than by spending all available resources on one technology at a time; except that in the very early stages splitting one's limited resources in this way would make achieving the first few advances a very slow process. There is a small random element in the number of turns required to achieve an advance; it may take one or two more or less than one would predict on the basis of simple arithmetic.

In each game each player is allowed to see a different random subset of the technologies at each level. On the other hand there are often alternative technologies that provide similar benefits. These features force players to adapt rather than follow the same favorite research strategy in each game. One can also make up for any important gaps by spying, technology trading or conquest.

Spaceship design

Ships can be used to colonize planets, scout for planets worth colonizing, attack other races and defend against attacks. Only six ship designs can be used at a time; a previous slot must be emptied (and all ships of that class scrapped) before a new class can be designed. Ships cannot be upgraded or refitted with new technology; the exceptions are discoveries that increase travel or scanning range, which automatically affect all ships.

There are four hull sizes; smaller sizes are harder to hit while larger ships can survive more damage and hold more components. There are eight types of components, each with different effects:

  1. Battle computers increase the chance of a beam weapon hitting and damaging a target
  2. Shields reduce the damage done by opponents' weapons
  3. Electronic countermeasures reduce the risk of being hit by missiles
  4. Armor determines the amount of damage a ship of a given hull size can withstand before being destroyed
  5. Engines power on-board systems, determine the speed of interstellar travel and a ship's maximum maneuverability during combat
  6. Combat maneuverability determines how fast a ship can move during battle and how hard it is to hit; maximum maneuverability is determined by the engine type used
  7. Weapons, being missiles, beams, bombs and biological weapons (biological weapons reduce a colony's population without damaging buildings)
  8. Special systems which have varying effects: improve a ship's range or maneuverability; improve weapon accuracy or range; provide defensive, offensive, repair or sensing advantages; a few "special" weapons, some of which affect whole stacks of enemy ships; colony bases are also considered special systems

Space combat and invasions

Ships can travel to any star system within their range and combat always occurs in orbit over a planet - it is impossible to intercept enemy ships in deep space. All ships of the same class form a single stack, moving and firing as a unit. Players can control space combat manually or ask the software to resolve combat automatically. Battles are almost always decided by numbers and technology rather than by clever tactics.

If the attacking player wins the space combat, the attacker may bomb the colony and, if invasion ships are present, they will try to invade it. Invading without destroying all defending ships and missile bases will result in the loss of some or all the invading ground forces and hostile planets can not be invaded unless attackers have the level of technology that allows them to colonize the same type of planet. There are no specialist invasion ships, invading forces are drawn from the population of one or more colonies, which reduces the population of the planet(s) from which they are sent.

Invasions are depicted in real-time but players cannot control combat. Results depend on numbers, technology and (if one of the races involved is Bulrathi) racial ground combat bonus. Invasion is expensive, but usually provides worthwhile advantages if successful: the production capacity of any remaining factories, plundering of technologies if enough factories survived the attack, and control over a new system that extends the range of the invader's ships. A successful invasion exterminates the previous inhabitants and the surviving troops form the planet's new population.

Races and diplomacy

Master of Orion has ten playable, pre-defined races that can not be customized (a feature available in sequels). Each race has a leader that players interact with and a default relationship with the other races that they will drift towards if not prompted by the actions of other leaders. Leaders each have a personality and determines interactions during diplomatic situations and objectives that influences their allocation of resources. Personality types include ruthless, aggressive, xenophobic, honourable, pacifist and erratic and objectives include diplomacy, military, technology, ecology, industry and expansion. Though each game will vary, race tends towards specific combinations of personality and objective and tendencies will rarely be diametrically opposed to a natural inclination. Leaders also adjust their behavior according to past actions taken by other leaders, even if they are towards another race (genocide, for example, causes all leaders to react negatively). A wide variety of diplomatic actions can occur between races including giving gifts, trading, paying tribute, spying, sabotage, alliances and wars. Finally, races possess an advantage in one area of the game mechanics and technology and some possess disadvantages.
Race Species type Advantage Technological advantage Technological disadvantage Diplomatic tendency
Klackon Insectoid Superior worker production Construction (excellent) Propulsion (poor) Xenophobic industrialists
Meklar Mechanoid Superior factory production Computers (excellent) Planetology (poor) Erratic industrialists
Sakkra Saurian High population growth Planetology (excellent) None Aggressive expansionists
Psilon Humanoid Superior research techniques All (good) None Pacifistic technologists
Mrrshans Feline Hit/damage bonus in space combat Weapons (excellent) Construction (poor) Ruthless militarists
Alkari Avian Superior space pilots Propulsion (excellent) Force fields (poor) Honorable militarists
Bulrathi Ursoid Superior ground combat Construction (good), weapons (good) Computers (poor) Aggressive ecologists
Humans Human Superior diplomats and traders Force fields (excellent), planetology (good), propulsion (good) None Honorable diplomats
Silicoid Geodic Ignore pollution and planet hostility* Computers (good) All other areas (poor) Xenophobic expansionists
Darlock Humanoid Superior spies and saboteurs Computers (good) None Aggressive diplomats
* Silicoids population growth is 50% slower than most races and 25% that of the Sakkra.

Random events

Master of Orion will sometimes produce random events which can be harmful or advantageous. Random events include discovery of ancient ships and technology, changes to planetary conditions that alter the planet's population or mineral richness, diplomatic blunders, changes to research, industry or treasury production, planetary rebellion, space piracy and attacks by space monsters that can destroy colonies. Random events can be disabled by means of a cheat code.


Master of Orion is based on its prequel game Star Lords, often called Master of Orion 0 by fans. Star Lords was a prototype and never commercially released (its intro opens with "SimTex Software and Your Company present"). The crude but fully-playable prototype was made available as freeware in 2001, stripped of all documentation and copy protection, in anticipation of the launch of Master of Orion 3. Major differences between Star Lords and Master of Orion I include inferior graphics and interface, simpler trade and diplomacy, undirected research, a lack of safeguards to prevent players from building more factories than are usable and the use of transports rather than colony ships to colonize new planets. One feature of Star Lords that Master of Orion lacks is a table of relations between the computer-controlled races. The game is available for download on FilePlanet and the home page for Master of Orion III.


Two commercial sequels to Master of Orion have been released, Master of Orion II: Battle at Antares and Master of Orion III. The sequels are significantly more advanced in graphics and sound but feature large differences in gameplay, with some players claiming the original game remains the best version of the three. FreeOrion is an open source, freeware game inspired by Master of Orion that has numerous similarities to games in the Master of Orion series.


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