The pitched battle system in Imperium has gone through many iterations; I can count four or five, just of the top of my head. And we’re talking of fully-fledged iterations; with the engine implemented and playable. Some of these have been good, others, less so. The key problem that has led to so much experimentation has been the need to find a battle resolution system that is both interesting and AI-friendly. In short, if you are facing AI-Hannibal, even with Scipio Africanus, you should be worried even knowing that you can influence the course of events…
The current – and final – version of the battle system is an auto-resolution system where the player’s general, army composition, and luck hopefully blend to give a satisfactory battle result. Several of the iterations I worked through were much more interactive, but they all invariably resulted in long playing times (a problem, given that 250 years will see a lot of battles) or impossible AI (which undermines the strategic game). The current system gives quick results, yet hopefully still provides enough interesting decisions to enhance the game narrative.
Pitched battles are resolved in three distinct phases: skirmish, clash, and pursuit.
In the skirmish phase, all the units assigned to skirmish as well as skirmish detachments are engaged in combat (a “skirmish battle” as mentioned in the previous post, is just this phase of the battle). An army will want to have at least one regiment of skirmishers committed here, as the main battle line troops may suffer casualties from missiles if the army’s skirmishers are completely overrun. The result of the skirmish may also impact the combat value of the units in the ensuing battle directly; units that are shot at and harassed while deploying into battle formation being unlikely to fight at their best in a pitched battle.
The clash of forces is naturally the high point of the battle. The regiments of each side are lined up against each other with the frontage potentially being constricted by the type of terrain present. The player has some limited control over how forces are lined up (strong right flank, left flank, center or perhaps a weak center) and allocates units between flanks, battle line and skirmish line. Units that have skirmished will participate in the battle, though their earlier exertions will mean that they fight at lowered strength even if they have not suffered casaulties. Needless to say, infantry units will tend to be more useful in the centre of the battle line than on the flanks.
Combat is then resolved with forces clashing “row by row”, starting with both flanks. If a force succeeds in routing its opponents, it may swing inward and take other enemy units in the flanks and rear. This mechanism makes it possible for strong cavalry units to be decisive if they are not neutralized (or at least blunted) by an opposing cavalry force. The battle is decided, however, by which side wins more of the clashes on the battlefield; it is thus, in fact, possible for a heavily packed infantry army to win even if it loses on the flanks (essentially, what the Romans tried – and failed – to do at Cannae).
Casualties are relatively limited in the clash of forces (typically 5 to 20%); the real problem occurs in the pursuit phase. As the word implies, this is where the winning side tries to inflict additional casualties on the losing side. The system is very simple, with cavalry and light infantry being more deadly than the heavy infantry. Regiments that have been outflanked or surrounded during the battle will suffer much higher casualties. A powerful cavalry force can wipe out its opponents in this phase.
So far, the results of the battles I have seen have been very satisfactory. The battle resolution system fulfills a number of key requirements that I aimed to see in the game. Heavy infantry are the king of the battlefield, but the cavalry have the possibility to be decisive. Missile troops (i.e. skirmishers) are neither simple support troops or paper in the cavalry-infantry-missile RPS trinity, but have an individual and important role on the battlefield. If the system works as intended, players will be encouraged to build armies similar to those that campaigned historically by the game mechanisms, rather than just for the fun of it.
Whether they do so, of course, remains to be seen. For now, however, this concludes my discussion of the combat mechanics. Hopefully, these posts have provided you some insights into the ideas and thoughts that have gone into the battle aspects of the game.