Injuries are fairly complicated things – and living bodies can be astoundingly durable and terribly fragile at the same time.
In a human being, a light thump on the chest – in the right spot and at the wrong instant of the heartbeat cycle – can cause near-instant death. A blood clot the size of a pinhead can easily kill. A common housecat could slice open an artery in your neck with a single lucky shot. Being stabbed with a pencil, a single shot from a .22, a blow from a swan’s wing, a severe allergic reaction, a small electrical shock – all of these things and many more can kill almost instantly.
On the other hand, humans – sometimes with little or no medical treatment – can survive tremendous amounts of punishment. People have survived free falls from thousands of feet without serious injury. They’ve lived through having multiple lengths of rebar impale them through the chest, having massive chunks of iron driven through their heads (search for Phineas Gage), and through many other horrific injuries. They’ve had arms ripped off at the shoulder in farm machinery, held a shirt across the wound, and walked back from the fields to call for help – and been at the door to let the ambulance crew in and direct them to get the arm.
And yes, that last bit is a personal observation; it happened to a farmer I knew decades ago.
In many of those cases, the difference between death by, say, nicking the aorta, or throwing a clot into the brain, and easily surviving a simple flesh wound, is a tiny fraction of an inch.
Now, when a human is injured, you get shock responses, pain – at least after the adrenalin rush and the endorphin release wind down – and a wide variety of disabilities. Such wounds may heal in short order, take lengthy periods to heal, or sometimes will result in permanent disabilities.
When people are moving around in a fight, most attacks are going to be opportunistic; you see a chance to get in a shot, and you take it. You can improve your odds of inflicting a serious injury by using more powerful weapons (that damage more tissue more greatly) and by aiming for areas containing vital organs, but you really can’t guarantee it short of resorting to weapons that can be counted on to destroy your target’s entire body.
If you want “Realistic Combat” you’re going to want some sort of table (in lieu of a computer simulation or resorting to actual fighting), providing specific injuries and their effects, each one with some estimate of how long it will – on a rough average – take to recover or die from, and with at least a modest chance of almost any injury being fatal.
There are games that do that. You can even do it in a page or two. For example, Baba Yaga does it that way (the players packet, with the wound tables and other basics, is a free download available HERE). Combat in those games is very dangerous, very exciting – serious gambling always is – and tends to be over fairly quickly. It’s something that wise players try to avoid, just as wise people try to avoid unnecessary fighting in real life. It leads to lots of careful planning and consideration of tactics.
That was why our Baba Yaga games, set in World War II, tended to have a lot less actual fighting than our fantasy adventure games often did, and why – when one side or the other found that their position was impossible – that side tended to retreat or surrender.
Realistic combat systems are usually a good choice for grim-and-gritty games and settings, for low-powered adventures, for games based on realistic wars and mercenary operations, and for horror games. They can, however, be rather disquieting; it’s not too uncommon for players to know people who have suffered similar injuries.
“Semi-realistic” combat systems almost always revolve around one basic mechanic: characters have some sort of abstract (and usually relatively small) injury track, often with various levels of wounds and a distinction between lethal and nonlethal damage (the basic system underlying games as diverse as Champions, Call of Cthulhu, Shadowrun, Classic Traveler, the various White Wolf Games, and Mutants and Masterminds) and offer characters the chance to evade and/or resist damage through various die rolls. Depending on how those die rolls are set up, characters may be anything from incredibly durable (Mutants and Masterminds) on through terribly fragile (Little Fears).
This discourages combat somewhat – the more fragile the characters, the more it discourages it – but means that characters with a higher-than-usual ability to evade or resist injury may resort to it fairly often. Characters may surrender at times, but even a modest edge or special ability may give them a chance to escape rather hopeless-looking situations. Such systems offer the advantage of relative simplicity, and usually of improved character survivability, but tend to become awkward when the question of specific injuries or long-term damage comes up. There are a few options for assigning long-term penalties, but doing so starts moving back towards the complicated-table option.
Semi-realistic systems are usually a good choice for espionage, low fantasy, and action movie games. You can even specify a few different tracks – say, for physical damage, stunning damage, damage to your life force, damage to your karma, and damage to your social life – and simply assign a few attack-and-defense skills to each. Go ahead, destroy your opponents social standing with lies and vicious rumors while they attempt to so badly damage your karma with maledictions and dark rituals that your life will become a hopeless misery and nothing will go well for you until you find someone who can undo the damage! Can you eliminate the evil merchants resources before his hired assassins take you out? Only the general combat rules know for sure…
“Unrealistic” systems tend to encourage combat, are usually quite abstract, have only a few damage levels if they consider the effects of wounds at all, and almost always revolve around some variant on the venerable “hit point” mechanic. In such systems characters can sustain quite a lot of injury, damage accumulates slowly, and there is little or no chance of a quick death unless the characters are totally outclassed by some major menace. Fights become contests of attrition, with tactics and special abilities coming in to play to see who can grind their way through their opponent’s hit points first. Characters who are losing will usually know it well in advance – and can either attempt to withdraw or bring more special abilities into play to avoid being killed. In most such systems, damage can be healed relatively quickly and easily. Any pretense of suffering specific injuries or of long-term damage will be an awkward graft onto the system at best, a clunky monstrosity at worst.
This also works just fine in a game, but suffers from a unique problem that dates all the way back to the early days of first edition D&D – attempts to explain the rules in “realistic” terms, usually by splitting hit points into separate pools representing “real injuries” and “ability to avoid real injuries”. Sometimes this is a formal rule, as in Palladium and Rifts, and sometimes it’s simply by claiming that characters with very large numbers of “hit points” compared to normal people are somehow evading injuries through some combination of skill in blocking, a learned knack for dodging, luck, divine aid, and other unexplained factors, rather than being “unrealistically tough”. In games which are usually full of characters who can cast spells, wield psychic powers, and pull off impossible physical stunts, this is roughly equivalent to swallowing Mount Everest and gagging on a grain of sand, but people do it anyway.
Since most such games make “hit points” readily restorable with basic healing magic, often make it possible for characters to determine (at least roughly) how many hit points they have left in the game (in d20 Deathwatch does this), and usually allow characters to resist things like falling into magma thanks to their high hit points, this doesn’t really work. How will healing magic restore luck and divine aid? How can one readily measure how much skill you have “left”? Skill does not gradually wear away like that; even the most skilled blocker could slip up at any time – and a fortunate idiot could hold out for hours.
Such attempts create far more problems than they “solve” as long as you care about consistency in your game world.
This is not to say that you can’t be very realistic about hit points – you just have to be consistent in terms of forces which operate in your game world. That often doesn’t have much to do with real-world biology or physics, and there’s no reason to pretend that it does.
In World Tree, “hit points” are a measure of how strongly your animating spirit can hold on to your body; a sword through the heart or arrow through the brain or near-total blood loss is annoying – but if your spirit is still hanging on, it can keep the body functioning – if at some penalty for the sheer quantity of damage.
In Continuum II, warriors are tapping into the same types of magical forces that mages are; they’re just channeling them into personal enhancements. They really may be far tougher than a steel statue – and blows that would cut a normal human in half will simply slightly gash a powerful warrior.
Perhaps characters with lots of hit points are so filled with life energy that they can ignore horrific wounds that would kill a lesser individual instantly. Perhaps “hit points” are a kind of bio-energy force field, that absorbs blows until it is exhausted.
Perhaps most of them are luck or divine aid or some such – in which case, you’ll want to break up “hit points” into separate pools, specify when each pool will and will not work, and provide a separate set of mechanisms (basic recovery rate, spells, powers, and other abilities) for restoring each pool. That’s rather awkward to handle, but can be quite interesting – and it can mean that, for example, mages can handle lots of magical damage, while thief-types can handle lots of damage from traps, clerics might be best suited for confronting evil spirits and undead, and so on.
Actually, I may write that up one of these days.
In any case, unrealistic systems are usually a good choice for high-fantasy games and for any game revolving around combat; if you’re going to have a lot of fights, and still want most of the characters to survive for more than a few sessions, you’ll want to stay away from quick kills and long-term effects.
Like it or not, the combat system you choose is going to say a lot of things about your game; you’ll want one that promotes the sort of game you have in mind, and which is internally consistent with your world. Nothing shatters suspension of disbelief faster than having your world running on two contradictory sets of rules – the ones you use to represent the activities of the characters and their major opponents and the unwritten ones that the world background runs on. Once the players start to notice that kind of problem you can say goodbye to any chance of them taking the world seriously or trying to figure anything out. Why should they bother trying to think when logic doesn’t apply?