Building Sphere of Influence Campaigns
A sphere of influence is a form of empire-building used in ancient Greece and the modern day whereby the imperial capital uses economic dependence, military alliance, and/or influence over the leadership of outlying territories to exert control without directly administering those territories. For example, Daggerford’s entire economy is based on trade with Waterdeep. If Waterdeep cuts that trade off, Daggerford will collapse. Waterdeep would lose the valuable link to Baldur’s Gate and Cormyr, but would be able to keep itself afloat off its trade with Neverwinter, Luruar, across Anauroch to the Moonsea and Cormanthor, and all along the Sword Coast using its port. This economic asymmetry means that Waterdeep has a lot of influence over Daggerford, and can make Daggerford do almost anything. Daggerford will do whatever Waterdeep says unless their relationship gets so bad that Daggerford would rather be destroyed if it meant they could spite Waterdeep on the way out.
Daggerford isn’t the only town in this position with Waterdeep. The Dessarin Valley, Triboar, Secomber, and others besides are similarly dependent. On top of that, all the Lord’s Alliance, covering the bulk of the Sword Coast and a few places beyond, have a military alliance with Waterdeep, which means they’d all like to keep Waterdeep happy enough with them to continue that alliance. Waterdeep doesn’t have nearly as much influence over them as it does over Daggerford, but it has some influence. Luruar has much stronger military ties between its cities, with Silverymoon effectively governing the other cities by virtue of the others being dependent upon Luruar for military support, even though their economy is independent by way of trade with the nearby dwarven strongholds of Felbarr, Adbar, and Mithral Hall. Zhentarim Keep, back before the Netherese razed it, controlled many Moonsea cities via planting infiltrators throughout the government such that the leaders answered to their hidden conspiracy even though the cities were all nominally independent. Economic dependence, military dependence, personal loyalty of the leadership, these are what make a sphere of influence.
Alright, so poli-sci 101 aside, why do we care? We care because a sphere of influence campaign allows for players to take over the world without doing an awful lot of mass battles. In a sphere of influence, players are more concerned with things like clearing ancient mines overrun by monsters that contain valuable treasures (the mines, not the monsters) in order to secure an economic treaty with towns in the area, winning the personal loyalty of the king of the next kingdom over by saving his kidnapped daughter from a dragon, and killing the champions of a rival power so that they can no longer guarantee the safety of an important border town, thus forcing the government of that town to turn to you for help or else be overrun by a horde of orcs headed their way (and also subsequently defeating that horde of orcs).
With the exception of the parenthetical, none of these are major battles, but all of them expand the section of the map that players control, and that’s a sphere of influence campaign in a nutshell. It has the advantage of being extremely flexible. Since you’re not occupying any territory, you don’t need an unbroken supply line to your territory which means you can jump all over the map as the mood suits you. Standalone adventures, whether published adventures or ones you made for earlier campaigns, can be slotted in wherever, and so long as the plot has serious implications for the military, economic, or political landscape of the area it takes place in (very likely), you can come up with a sphere of influence-related plot hook and you’re golden.
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