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.
Building a Sphere of Influence
Each nation on the world map has one of six attitudes towards whatever nation the players control. From most to least positive attitude, these are occupied, military alliance, trade agreement, neutral, closed borders, and at war. The goal of the campaign is typically to have every nation be at least neutral or better or else to have a certain number and/or specific list of nations have at least a trade agreement. For example, a Faerun-based sphere of influence campaign in which the players control Waterdeep might have the goal that all nations be at least neutral, necessitating that something be done about Thay and Calimshan and so forth, or else that at least nine of Waterdeep, Baldur’s Gate, Silverymoon, Neverwinter, Amn, Calimshan, Cormyr, Hillsfar, Halruaa, Chessenta, Mulhorand, Aglarond, and Thay be a trade agreement or better, in which case the players don’t necessarily have to defeat all of Waterdeep’s greatest enemies (and the biggest threats to Faerun in general), just enough of them to become a dominant power on the continent and defang any remaining hostile nations. Perhaps instead there’s a specific list of targets who must be brought into the sphere of influence with a trade agreement or better, like Amn, Thay, Hillsfar, and Menzoberranzan.
Convincing a neutral nation to enter into a trade agreement or military alliance is just a matter of coming up with a relevant adventure and then the party goes there and does the adventure. For example, in the Lost Mines of Phandelver the party secures a valuable mine and makes friends with the dwarves who run it, which gives them all the leverage they’d need to convince the Triboar Trail to enter into a trade agreement with them. In the opening to Rise of Tiamat, Greenest is the latest victim of the Dragon Cult’s raids through Greenest, and the party might deal with the raiders as a show of good faith in order to convince Greenest to make a military alliance with their own nation (and then that simple raider hunt turns into a plot to save the world, but you can cut down the scale of the raiding if you just want to use the first few chapters as an adventure to turn neutral Greenest into a member of BLUFOR).
Rather than having adventures associated with them, some nations might not have any troubles best addressed by a band of 3-6 very strong people stabbing things in the face, but they’ll still be part of trade networks and if enough of their trade network joins a trade agreement, it starts to become very foolish for them not to sign onto that agreement. For example, Phlan, Hillsfar, Thentia, Mulmaster, and Melvaunt are all part of the Moonsea trade network. If three out of those five cities all joined a trade agreement, the other two would probably follow – unless one of those two is Hillsfar, who are striving to establish a sphere of influence of their own over the Moonsea and can’t be bribed into giving it up.
This brings us to dealing with hostile nations. Generally speaking, a nation attempting to build their own sphere of influence will close their borders to rivals, and a nation who’s closed their borders are far less receptive to signing treaties with helpful adventurers. Some of them might be brought to the negotiating table by sufficiently lucrative trade deals, but the majority are going to have to be dealt with through other means. Nearly every throne in the world has someone or other who thinks they deserve to sit on it more than its current owner, and who’s willing to stake their life on making it happen. Backing these pretenders to the throne can put someone much more sympathetic on the throne. In many cases, this will be someone who’s willing and eager to sign an immediate military alliance. In others, the only viable pretender the party can find might plan to take a neutral stance and stay out of the (potentially cataclysmic) clash of titans that’s brewing altogether. Sometimes it may even be a radical isolationist who plans to close the borders entirely, but at least they’ll close their borders to both the party’s nation and their rivals. Tchazzar, the mad dragon who claims ownership over Chessenta but has been exiled to the Sea of Fallen Stars, is probably not going to be particularly friendly to Waterdeep, but at least he’ll be equally unfriendly to Thay.
If assassination and/or internal rebellion aren’t an option, there’s always outright invasion. The players might not be able to convince even allies with a military alliance to participate in an aggressive action, so even when players have 60% of the map in their sphere of influence, they can’t necessarily pose an overwhelming military threat to literally every nation outside that sphere. Players who’ve locked down the entire Sword Coast down to Calimshan, for example, might still find themselves locked in a pitched battle with Hillsfar, just because Silverymoon and Neverwinter and other powerful allies won’t send troops to invade a distant city. Even though Hillsfar is full of xenophobic imperialists who no one on the Sword Coast would want to be neighbors with, they aren’t neighbors, so they’re probably happy to let them be someone else’s problem. All this to say that mass combat adventures to invade hostile nations aren’t necessarily a foregone conclusion just because it’s the endgame and players control a lot of the map.
Supply Centers and Lieutenants
Hostile spheres of influence don’t sit around waiting to be toppled. What distinguishes them from isolationists or neutral nations is that they, too, are attempting to expand their sphere of influence. An enemy sphere of influence – we’ll call them REDFOR – has at least one supply center, which supplies one lieutenant. This lieutenant can attempt to convince neutral nations to join their sphere of influence or foment rebellion within the party’s own sphere of influence just like they can. For example, a lieutenant of Szass Tam might be sent to Kryptgarden Forest to convince the creatures there to join forces with Thay, placing a powerful enemy on Waterdeep’s doorstep. The party must then choose whether they’re going to try and foil the lieutenant and preserve the sphere of influence they already have, or go on a quest to expand it.
REDFOR will usually have just one supply center, but if they have two, that means at least one of their lieutenants will be completely unopposed in their nefarious work. Fortunately, the party’s sphere of influence is not completely unable to look after itself. Each nation has a DC between 5 (for a place that’s practically in anarchy already) to 30 (for a superpower nearly impervious to subversion or attack). Most nations have a DC of 15 or 20, with 15 representing a nation that’s just a bit on the weak side and 20 just a bit stronger than average. Bear in mind that the most famous nations and city states of a setting are not average. Baldur’s Gate and Waterdeep are at least a DC 25 and very possibly a DC 30 to subvert, while DCs 15 and 20 better represent places like Elturel, Cormanthor, and Icewind Dale. DCs 5 and 10 should be reserved for sparsely populated areas like the Triboar Trail or places that lack a unified will to resist outside influence like the Border Kingdoms on the Lake of Steam.
Each REDFOR lieutenant has a bonus to subverting nations that will be between +2 and +17 depending on their competence, with most gravitating towards a +11. An unopposed lieutenant rolls a check against the DC of the nation they are attempting to subvert, and if they meet or exceed that DC, they succeed. Just like the party, they might not always be able to get exactly what they want, perhaps installing a ruler who washes their hands of both sides or causing the place to collapse into a useless anarchy instead of installing a ruler who signs a military alliance with REDFOR. At minimum, if the lieutenant was targeting a BLUFOR nation, they will have left BLUFOR, and if they were targeting a neutral nation, that nation will join REDFOR. If the lieutenant fails his check, he is defeated and cannot be deployed by REDFOR until they regroup. Win or lose, the havoc caused by the lieutenant usually decreases the subversion DC of the nation by 5 points.
D&D has a revolving door afterlife. When the party confronts and kills a lieutenant backed by a powerful enemy with mid- or high-level clerics and plenty of gold, it’s usually not the last they’ve seen of that lieutenant. Even if the party takes pains to make sure the body stays out of enemy hands and REDFOR doesn’t have a high enough level cleric to can raise someone without a body, it’s only a matter of time before REDFOR finds a replacement. However, whether they’re recruiting a new lieutenant or waiting for the old one to walk off their injuries/death, REDFOR does have to take time to regroup and reorganize their defeated lieutenants before they can deploy them again, finding new targets, arranging very long range transport (even if they can teleport, they’re rarely familiar enough with places very far away to teleport there safely), and concocting new schemes. A defeated lieutenant remains defeated until REDFOR takes the time rally them, and during that time REDFOR cannot use any of their other lieutenants (if they even have any) to advance any other schemes. Players have a chance to go on a quest to advance the interests of their own sphere of influence without having to worry about attacks. Regrouping like this only restores one lieutenant to ready status. If REDFOR has several lieutenants and wants to restore all of them to ready status, they must give the party a chance to go on an adventure unopposed for each defeated lieutenant they wish to revive. Powerful enemy forces with several supply centers can be relentless while they still have lieutenants to spare, but they’ll be dormant for a long time regrouping after the party finally hacks through all of them.
The party can have lieutenants of their own. The first supply center they capture is used for the party themselves, but if they capture a second supply center, they gain a lieutenant. Just like a REDFOR lieutenant, the party’s lieutenant can be sent to neutral or hostile nations, rolls his subversion check against the nation’s DC, and if the lieutenant succeeds, then at minimum a REDFOR nation will leave REDFOR and a neutral nation will join BLUFOR. Just like REDFOR, BLUFOR lieutenants who fail their checks are defeated, and the players must spend a turn regrouping their subordinates in order to bring one of their lieutenants back to ready status, during which time neither they nor their lieutenants may undertake any missions. If REDFOR isn’t regrouping at the same time, they will be able to act unopposed.
Some lieutenants are particularly skilled at using intrigue, mercantilism, or war to bring down a nation, and likewise some nations are particularly resistant to or weak to certain methods of subversion. A lieutenant who is particularly skilled at a method that a nation is weak to gains advantage on their roll, but one who is particularly skilled at a method their target nation is strong against takes disadvantage on their roll. Not all nations or lieutenants necessarily have to have these strengths and weaknesses.