The Interactive History concept was introduced by the Aria gameline. The idea was that instead of persons (or in addition to persons) the players would play whole societies. The way this differs from for example playing Civilization (or any other game of strategy) is that the culture is given the highlight. The rules given by Aria for IH provide a rough way to resolve military, but also and more importantly social and political conflicts. The results are also highly interpretative: to really work they need to fleshed out by the players and the GM. This means some work, but when done, it gives a highly enjoyable gaming experience!
The dice system provided by Aria is a bit obscure, and for this and other reasons I decided to try to convert the IH mechanics to FUDGE. Other than that, I have tried to correct a defect of the original game, namely that it does not directly faciliate playing different levels of a society at the same time, e.g. one player would play the ruling agency and the others would play the key persons of that society.
In short, the idea of interactive history is to let each player play the governement, or the ruling agency, of the society of their choice. Besides nations, the players may choose to lead another kind of societies: secret societies, or a church. Or he may play key persons in the game: master tradesmen, powerful barons, heroes or saints.
The player has several options to do. He can
The flow of game is divided to rounds, with each round equaling 1, 5, 10 or any other number of years, as decided by the GM. Each round is divided to four phases: events, internal development, external development and resolution phase.
In the event phase each society rolls for an environmetal disaster (10% chance, or a -2 on 2DF). Should any occure its results are determined at once. The disaster is always assumed to be worst of its kind, so the task should be appropriately difficult. The skill base is the scope of the society + 1, and the task level should be at least Very hard. The results from a disaster can never be positive: they are always regressions of some kind or another.
In the internal development the actions within a society are declared. If there are any situations which require immediate resolution, e.g. so-called critical junctures, they are resolved immediately. The external development is similar to the internal development phase, except the actions concern other societies.
The last phase is the resolution phase. The declared actions are resolved in an appropriate order. The results result in regressions (some attributes drop), improvements (attributes increase) or incidentals and reactions (minor changes). The GM does most of his job at this phase.
Each society will have certain attributes, which tells us something of the society. The attributes may be roughly divided to three groups: political, cultural and societal attributes.
The political attributes detail the abilities of influence that entities have in that society. Primarily the political attributes are defined for the ruling agency, but you can give political attributes to others as well, for example each key person or organization. However, it should be noted that ruling agency should always have the greatest degree of power and authority. Otherwise it wouldn't be ruling agency, would it?
The cultural attributes detail the culture of the society. Its basic philosophy, the variety and importance of different humanities, and its available technology.
The societal attributes detail the abilities and resources of the society as a whole. Its scope, military browess and economical resources.
The military power and size depend on the scope of the society, but also from its philosophical orientation and its military structure. Combined military power and size give the military browess of the society.
Players may also play something else besides ruling agency; smaller societies (secret societies like free masons, or churches) or single individuals (key persons, heroes, saints). The key persons will have lots of political influence (although not as much as the ruling agency). The heroes will have some exceptional abilities, for example 'strategist' to gain +1 to all war related actions, or 'Machiavelli' to gain +1 to all intrigue attempts. The saints may also have some exceptional abilities, like 'guru' to gain +1 to all influence actions, or 'mystical powers' to gain +1 to war related actions or whatever.
If the task is clearly too easy (or too hard) for a person, the social effects of success (failure) are limited appropriately. For example if a person with a superb skill attempts an easy task, rolls a 0, and scores a superb success, the social influence is limited to the equivalent of a partial success, since the result was what everybody expected. Similarily if a person is forced to attempt something far out of his ability and fails, the attempt has only slight repercussions (partial failure), since nobody really expected a success. If the task was not forced upon him, a stupidity modifier is applied...
I have found that the most work is not to invent what happens in a given society, but rather what happens in the other, non-player societies. I think a suitable way to handle them would be to roll them events in the events phase, something along the lines: disaster, economic depression, civil war, revolution, raid, war, change in philosophical orientation, and not care too much about the details.