I think its pretty obvious that the civ4 AI is lacking in many areas when it comes to holding together a successful war. A major, major issue is a country that does not have access to oil that attempts to conduct a war with a civilization that has access to oil (or even warring with a civ that currently TRADES the oil to them). The outcome here, is without a question a bad decision and loss for the country without oil. The bottom line: In today's world - ANY country that wants access to oil can get it. With that knowledge: Every country should have access to oil because even if it was embargoed from one country, another country would gladly corner the market and sell it to the embargoed country at a premium (or gift it to them to aid a war effort) in real life. And trying to mod that into the game code is simply not exactly feasible, and it will not work correctly. (Yet, I do have an idea for a simple new unit to make this even more realistic further below...) Trying to "demand" the AI to trade with each other, or attempting to program the AI to "know to have oil during a war effort" is not going to happen because the Civ4 mechanics do not allow for that, at this point in time. So, without adding more complexities to the game-code that simply will not work correctly (or at all), and will slow the game down, we should simply have every country always have permanent access to oil (please read on for the idea about oil embargos, though!): <---AND WITH THAT: -*Idea* - Since I think every civ should have access to oil for game coding and AI usage simplicity [since the goal is to make the AI able to actually PLAY the game well against us] and not try to have this glorious thought we can actually program the AI to do this correctly, because Civ4 is not quite advanced enough for that, yet, we should create a new unit/unit option: As a naval ship can "blockade" enemy tiles from obtaining resources and trade routes, we should have a land unit that can "blockade" land area/land trade routes in the same fashion - this unit/unit option would streamline a lot of things into a simplified choice for the AI and negate programming that the AI may never even use. We know this should work, because the AI consistently uses naval blockades very well. Obviously while the land is being blockaded, the affected cities will not be able to produce oil units until the blockading vehicle(s) is destroyed, allowing oil to once again be available to the city. It will A) make the mod more realistic because in reality, all countries can get access to oil whenever they want - because even during embargoes, someone would sell it to them for heavy profits, and B ) make the modding more simplistic as creating a land unit based on the blockade the sea units can do should be fairly simple programming.