There are a lot of fictional settings with some sort of war taking place predominantly in it, where there are various skirmishes here and there along contested lines of combat. Various fantasy movies from 300 to Lord of the Rings to Chronicles of Narnia and even Star Wars have large battles taking place as cinematic events, while we have no shortage of war movies from those of World War 1 and 2 up through Vietnam and the Gulf to Iraq. Most of those movies use the war as a backdrop instead of the main focus. If it was the main focus, we would be playing war games like Diplomacy, Risk or Crusader Kings. Using the war as a backdrop gives us an environment where the adventures of a small group would take place and then we can tell their story.
There are a few ways that we can have this story be war focused without bringing the whole war into things and having the players fight wave after wave of troops. One example of how it could work could be seen in the video game This War of Mine, where the player deals with scavenging for resources in a war-torn country as they attempt to survive until the end of the war. Another example is Forgotten Realms: Demon Stone, shaping your adventure with the war going on around them, as you can see in this playthrough of the first level. Of course, since this is the first level the war is predominantly featured, it does get somewhat quieter as things move on. This is the sort of scenario we are focusing on today.
The D&D 3.5 book Heroes of Battle does a great job of going into detail about war style campaigns, so it is definitely worth a read if you want to add war in the plot and still let your players be active. I will generalize some of it here as well as giving my own ideas to the concept. In the end, the idea of a war campaign in tabletop style usually is getting away from players commanding whole units like the wargames D&D was based on and instead boiling it down to a small adventuring party style, much like a squad in a war movie like Saving Private Ryan, The Guns of Navarone, the Dirty Dozen with each character bringing specific skills to the table to aid the unit like we see in the tv series and movie The A-Team or the movies and 3D animated series of Starship Troopers. Rogue Trooper, Jagged Alliance, SWAT, Rainbow Six and Republic Commandos are video games where this is the core mechanic. Metal Gear style games are alright for a solo operation, great for those days you have most players unable to play and still want to run something, and you can bring other players in at later times as undercover agents, traitors in the enemy lines, captured soldiers or even a civilian standing against these oppressors.
One of the big driving points in a war game is why the players are together and what is driving each of them to go on this mission. Are they volunteers, mercenaries, bystanders sucked into the war, or were they drafted? Are they using a chain of command where one of them is the leader or do they work instead as a team? Are they motivated by their country service, out to protect their friends and family, fulfilling a contract for pay? Once these questions are answered, the group will have an idea of how to react and you will know how to use them.
The next thing that the Gamemaster needs to decide is how to apply this unit on the field. The majority of war movies I have seen focus on a few key objectives as the goal of the unit. Cutting enemy supplies or reestablishing your own, slipping past a siege to bring back reinforcements, destroying enemy emplacements (war camps, siege weapons, etc), exchanging prisoners, escaping enemy territory, rescuing prisoners, taking control of some terrain, protecting a target, or converting an enemy city. The enemy force in most of these is going to be like those you would see in a dungeon raid, though, depending on the enemy, they may be using tactics instead of just charging in.
One type of mission I did not see in Heroes of Battle and could be interesting to see in gameplay was the converting an enemy city. This is when soldiers come into a city in hostile territory and need to find a way to get supplies and possibly a place to hide. Invading armies can try this tactic and it is especially likely if the campaign is a liberation mission such as seeking to depose a corrupt ruler. Through propaganda and disinformation or just diplomacy or bribery, the players will need to make some allies in the enemy city that will provide them supplies, information, safe residence, or whatever else they might need. I would recommend anyone interested in a campaign like this check out GURPS: Social Engineering, as it is a great supplement to any game focused on using social skills in a greater fashion than in the main books of their system since most don’t give it much thought. For a visual example, watch this trailer for Wag the Dog to see how it just takes a decently presented story to get people to believe anything.
In order to make the campaign realistic, I suggest that any GM using a war backdrop to their campaign has an idea on how the war will play out up to its end. With each mission the players take part in, whether they succeed or fail, there should be some change in the major war taking place around them as battlelines get redrawn as armies advance or fall back. If the gamemaster decides the war was one ruler wanting to claim the lands of another by sieging their fortress, eventually the invaders will be beaten away or the defending side will crumble and be overrun. Perhaps after a mission the players return to their war camp and find it destroyed meaning they now need to find the new rally point while now in enemy territory. Maybe the players are successful in aiding their ruler that they are awarded some lands in the newly conquered domain, turning the game from a war theme to a more courtly theme as the players try to curry more favor from the ruler. By knowing what will happen when your players win or lose, you make things much more dynamic and realistic as the players see the results they are having. One great inspiration for this may come from war series, such as the animated series Starship Troopers: Roughneck Chronicles or Clone Wars, or one of these 10 animes. There are also shows like Band of Brothers or war movies like those listed earlier in the article, but I tried to stay away from realistic depictions of blood and gore as not everyone likes that. Basically, you want to think of your campaign like a Risk board and how the story would change with the win or loss of any territory, such as this map of Khorvaire from Eberron.
As with the example of the players coming back to find their headquarters has been overrun, do not be afraid from time to time to have the players be successful but the rest of the army fail. Your players come back to camp after taking out an enemy’s forward camp on a hilltop only to find out that the main unit was flanked and has taken some heavy losses. The players pushed the border forward on their side while it may have held or fallen back on another side. This can spur new adventures such as shoring up a falling line or changing their attack to the newly weakened front. Games like IL-2, a military airplane simulator, had dynamic campaigns that would allow the players to develop such storylines as the random campaign system figured out what the player’s results did and other variables for the rest of the front line.