For example, the game could have 2-8 player multiplayer. Every game would have 2-4 alliances (samurai, viking, knights, etc) and each player has to choose one and work cooperatively with their alliance members. Games could be divided into a 4 vs 4 game with two alliances, 2 vs 2 vs 2 vs 2 with 4 alliances, or any other variation. During the game each alliance would take turns managing the cities they control, with each player responsible for their own cities. Maps will be randomly generated along with resources. Depending on the buildings they choose to construct, the unit types and equipment availability will be different for the armies you construct.
Whenever a player instigate a battle, all the players who are a part of the competing alliances would also be involved with the battle. Either as a general or a random soldier. Army Size and unit types in the battle would vary depending on what each player had at the moment. The objectives of each battle will vary depending on where the fight is taking place. It could be to take over a city, stop an army on the game map, or just to harass other players by destroying their buildings. Spoils of the battle, such as captured units, gold, or cities will be given to the player who instigated the battle. OR if more than one player instigated a battle, then they can decide who gets what, perhaps by trading or sharing profits.
The overall objective of the game would be to wipe out all other factions, capture the capital, or control the most cities within # of turns.