Master of Orion II: Battle at Antares/Walkthrough

This set of pages covers a wide range of topics related top strategy and tactics. The content is mainly oriented towards multi-player games against other people, who are much trickier opponents than the AI. These techniques will generally also provide the quickest way to win against the AI; but, once you've become familiar with the game, it might be a good idea to use AI games to experiment with new approaches - and perhaps to add them to this guide.

Most of the contents of the guide are in separate pages - see the navigation links on this page or the Table of Contents.

Victory conditions
There are three ways to win:
 * Eliminate all enemy empires. This is usually the only route to victory in multi-player games. It does not necessarily require genocide, as opponents may be eliminated by various combinations of:
 * Exterminating colonies. This can be done in 3 ways: bombard the colony with bombs or biological weapons after winning a space battle; use a Stellar Converter (the most powerful of all weapons) to disintegrate the planet into an asteroid belt; kill off a conquered population at a rate of 1 unit per turn after a successful invasion (this option is not available to empires with Democratic or Federation governments); transport the population to colonies that are already full, so that they die on arrival.
 * Invading colonies and integrating them into your empire. Integration is called "assimilation" in the game and takes time, since the conquered population are initially all angry. Before a population is fully assimilated it's productivity is lower (but never less than about 50%). If less than 50% are assimilated there's a risk that they may rebel and re-join the empire that founded the colony - if it still exists; once that empire is eliminated, there's no risk of rebellion.
 * Another empire surrenders to yours. Surrender is quite rare, and surrenders to your empire are even rarer - when AI empires surrender, it's usually to other AI empires. If another empire does surrender to yours, it's likely to be a mixed blessing as the surrendering empire will be in deep trouble - usually it's in danger of being exterminated and / or its finances are a hopeless mess and / or it can't feed its population. But at least you won't have to worry about assimilation and rebellion. So you should be able to get your new colonies working well in about 10 turns and then the freebie colonies give you a big advantage.
 * Get elected as the supreme leader of the galaxy. To get elected as the supreme leader, you need two-thirds of the total votes (abstentions count as votes against both candidates), and each empire's votes are based on its population. It's very unlikely that peaceful colonization and economic development will give you sufficient population to win an election on your own, so getting elected requires some combination of conquest and diplomacy. Conquest is the more usual route because at the higher difficulty levels other empires will turn hostile if they think you are likely to win an election. Even then it's rare to win by election as the game software reduces the frequency of elections if you're winning.
 * Conduct a successful assault against the Antaran homeworld (via a Dimensional Portal). Other empires are so awestruck that they surrender immediately. This is possible but usually forbidden in multi-player games.

Despite the game's name, conquering the Orion star system does not automatically win the game.

The game's scoring
MOO II presents a score at the end of each game, and enters your ruler's name in the Hall of Fame if the score is in the top 10. Beginners may find the scoring helpful as a measure of their progress. But it's a waste of time and energy to go all out to maximize your score:
 * 1 point is deducted for each turn played.
 * 1 point is added per unit of population in your empire, with a bonus for populations of captured colonies (as at the time of conquest).
 * So to maximize your score you have keep playing until you've conquered / colonized all but one planet and all your colonies are at maximum population (after all possible terraforming projects are completed). This means playing for about 100 extra turns after you could have finished the game.