As varied as the typical periods of wargames are, the rules used for each period diverge even more. Practically each historical period, fantasy or sci-fi setting has several prominent rule systems and even more minor variations. The following is my personal high level classification of the major system types:
Simulations endeavour to, well, simulate actual activities on a wargaming battlefield to the highest degree of authenticity possible. To this end they are often based on numerous look-up tables and rules that are very heavy on mathematical equations (the only logical way to impose some form of system on highly complex events). Simulations are fairly common in the historical genre and most often encountered in 20th century games (i.e. World War 2, Modern, etc.). You know you have encountered a simulation in progress if you walk past a table and hear words such as “My Tiger tank shoots its main 88mm gun at your Sherman. The distance is long, my gunner is a veteran, my gun sights have the 1944 upgrade so that cancels your medium-fast movement speed, I am firing stationary and aim at your turret, I am using armour piercing rounds with the improved 1943 shaped charge head against your angled front turret armour…….”.
As a result of being wedded to authentic simulation, these games often take days to complete and in effect tend to run longer than the real world events that they aim to simulate. Simulations have always been at the extreme end of the wargaming hobby in terms of popularity though their small following is often fanatically loyal.
Kriegspiel is the German word for “wargame” and associated with the historical origin of the hobby. Used as a training and strategy tool by the German general staff since the 18th century, military wargaming is now a staple of higher level command training in most armies of the world. As with its professional counterpart, the Kriegspiel hobby systems focus on the overall military effect of a particular activity rather than an exact simulation of specific events. Historically, the earliest Kriegspiel rules would see people announcing their intention (e.g. “My light regiment flanks that line regiment on the hill”) and an umpire would simply decide the outcome of the action. Hobby systems of this type need to provide some fixed mechanisms to make these decisions but the complexity can be incredibly low. De Bellis Antiquitatis (DBA) is likely the archetypical representative of this type of wargame. Little blocks of two to four miniatures represent large formations and carry only a single descriptive specification (e.g. “Light Horse”, “Warband”, etc.). When such blocks meet in combat a single die roll with a few simple modifiers is used to decide the outcome between only a few options (e.g. “Destroyed”, “Retreat”, etc.). Everything else, such as casualties, morale, equipment, training and so forth, remains completely abstract. What matters is that cavalry will beat infantry on open ground most of the time, while Longbows tend to slaughter cavalry – regardless of any of the other factors. As simplistic as this appears, some of the best Kriegspiel systems are tuned finely enough that they tend to very accurately replicate the net outcome of real world engagements – cavalry after all WAS king of the plain until the English archers arrived.
Some slightly less abstract systems in this category are Games Workshop’s Warmaster (10mm Fantasy) and Epic Armageddon (6mm Sci-Fi), Osprey’s Field of Glory (15mm Historical), DBA’s big brother De Bellis Multitudinis (15mm Historical) and Hordes of Things (15mm Fantasy), as well as arguable Battlefront’s Flames of War (15mm World War 2). While Epic Armageddon and Flames of War feature individual models in a 1:1 representation with the actual soldiers, they base these in larger groups and retain many of the abstract features of the Kriegspiel. All these games use some form of command and control system to give a sense of realistic strategic limitations (not every unit can act all the time) and abstract the ground and time scale to some degree (units can move and engage over distances that are not linearly consistent if you think of one “turn” as a fixed amount of time, instead, one “turn” represents a period of activity that varies for unit to unit). The net result is that the overall tactical or strategic actions of the unit matter, not the details. Fans of this genre consider this emphasis on strategy rather than mechanics to be the corner stone of this type of game.
These game systems impose a higher level of detail on the fluid world of the Kriegspiel. Abstract blocks of soldiers remain blocks but are now resolved down to individual models. Movement speeds, actions and engagement ranges are reduced to a scale where turns roughly correspond to a consistent period of activity. By necessity this reduces the scale of engagements to a company level (hundreds of models representing individual soldiers). The most prominent example of this style is the Warhammer series of games including the popular Warhammer Fantasy Battle (28mm Fantasy) and the different variants of Warhammer Historical (28mm Historical), as well as War of the Rings.
This system often leads to chess-like game dynamics from the fact that the 1:1 represented blocks of units have very limited operating freedom in the game. The fixed time and ground scale means that individual blocks can cover limited ground in each turn so that their options are restricted similarly to chess pieces (though they still operate on a battlefield without squares). A typical game of Warhammer sees blocks of infantry and cavalry spending the first half of the game moving into position followed by the crash of opposite units into each other in the second half. Game winning plans resolve not so much around sweeping strategic manoeuvre but rather around the tactical aspects of positioning units at the right angles, creating setups for flank charges and so forth. Add to this a high degree of predictability of the (limited) movement of your opponent and the game play becomes very similar to chess (though still with dice).
Systems of this type lower the resolution of the game system event further by breaking blocks of units into individual models that act individually (though sometimes still constraint by some form of unit cohesion). The most common examples are 28mm systems such as Games Workshop’s Warhammer 40k (28mm sci-fi) and Lord of the Rings Strategy Battle (28cm fantasy), as well as Warmachine (28mm sci-fi) . Many of the other aspects of the rule systems of checkers style games are similar to their chess style sister systems (e.g. Warhammer 40k and Warhammer) which often leads people to erroneously assume that the game systems play similarly. The major difference lies in the breakdown of blocks into individuals. Regardless of other rules similarities, this causes a completely different type of game play. First, individual models tend to be able to move without any of the restriction of blocks of models in the chess style systems. Second, the removal of blocks has a force multiplier effect for each action (i.e. assaults, shooting, etc.) because all models on the tabletop can now participate in the actions rather than only the front rank of a block. As a result, units can move practically everywhere and bring massive assault/firepower to bear on opposite units. This creates a game play experience very similar to checkers where units are more or less placed somewhere, remove an opponent piece only to be removed in turn if another opponent unit appears, and so forth. Winning game play in such systems is pushed heavily into the meta-game domain of army list planning (bringing the right checker pieces to the game so to speak) and initial deployment (the placing of the checker since most of these systems often allow deployment practically everywhere on the tabletop by means of reserve, airborne, teleporting or other non-traditional placement options).
Skirmish systems sit on the extreme end of this spectrum and continue the trend of individualization to the point that each model is a fully independent entity. Often this results in the reduction of the game scope to a level below unit organisation (i.e. less than platoon/squad size). At this scale individual models often assume roleplaying-like characteristics with skills, equipment and even experience gains between campaign gains. Common examples include Games Workshop’s Mordheim (28mm fantasy), Necromunda (28mm sci-fi), Man-o-War (fantasy naval), Battlefleet Gothic (sci-fi starship) and story line games like Lord of the Rings (28mm fantasy). Skirmish games tend to remove strategic game play altogether with an emphasis on tactical considerations for individual models instead.