In Victoria 3, war is a means to an end. That end being economy and politics, with war being the final alternative. However, when it is being waged, it is done on Fronts.
In Victoria 3, rather than manually moving armies around the map, you assign troops, via Generals, to the border provinces where two combatants clash. All combat takes place on these Fronts, where a victorious outcome consists of moving the Front into your enemy’s territory while preventing incursions into your own.
Fronts are created automatically as soon as two countries begin to oppose each other in a Diplomatic Play, and consist of all provinces along the border of control between those two countries. Therefore a Front always has one country on either side, but it is possible for Generals from several countries to be assigned to the same Front.
In a large end-game conflict, you might have hundreds of thousands - possibly even millions - of soldiers in active service, which is a lot to keep track of. The number of active Fronts, however, is likely to be much more manageable. The design philosophy here is the same as with the economic Pop model. Our aim is to make the game playable and well-paced, without requiring frequent pausing, on every scale while retaining the detail and integrity of the Pop simulation.
For warfare, the scale ranges from a small border skirmish between minor nations in single-player to a massive multiplayer world war involving every Great Power. Using the Front system we can account for every individual Serviceman and Officer in meticulous detail while giving the player a high-level strategic interface to monitor and manipulate. Much like with the economic interface of Buildings or the political interface of Interest Groups, from this Front view, you can drill down through your Generals all the way to the individual Pops that actually do the fighting if you want to.