Hit points evolved from the game Battleship? Close.
this interview traces the concepts of hit points (and armor class, for that matter) back to when he exapted his US Civil War ironclads rules to represent heroic characters in a skirmish game. Both this system and the Milton Bradley system are great to model floating hulls that can take only so much structural damage before sinking.
And by the way, the "hit or no hit" way armor works in D&D also comes from this simulation of a floating hull where the armor is part of the structure. A shell either bounces off or penetrates it. There is no partial damage reduction because there is no meaty interior to the armored shell.
So, all you 8th level fighters are running around absorbing hits like the Graf Spee. Ridiculous, from a simulation point of view. But perfectly adapted to a gamer's need to act heroically - and that, in the end, is why hit points won out in gaming over limb-maiming and eye-gouging wound systems. Arneson even noted that a main reason to adopt the battleship system was to protect heroic characters from the instant, low-probability death possible under the Chainmail rules.
The hit point system means you are a hero at full fighting capacity right to your last gasp. It doesn't wear you down in a death spiral of diminishing returns. And it's easier to choose your battles, withdraw from a hairy situation, know when you've had enough.
More realistic combat systems hold open the possibility of random death or disablement with every blow. With smart players, this can make for an interesting game. It deters players from going into combat with weak creatures just to rack up experience points; makes them afraid to fight and eager to embrace alternative solutions. But sometimes you do want a game where characters fearlessly fight on, and hit points help that along.
My preference is for a game system that hedges its bets, combining these two features in a fair and fun way. Early on in D&D, house rules often adopted critical hit systems to make combat more realistic and deadly - the most influential of these being Iron Crown's Arms/Claw Law which would later evolve into the Rolemaster system. These also seem to be inspired by the critical hits found in some naval warfare systems, simulating lucky shots that blow up a ship's powder magazine or kill its captain. All very well when you have no personal investment in this or that ship. But the problem, as Gygax astutely notes in AD&D, is that spearing monsters through the eye may be fun, but having your own heroic character speared through the eye is not so fun.
The alternative Gygax proposed was a system of critical injury at zero or negative hit points, where player characters could still survive but were in danger of bleeding out at -10, losing 1 hp/round. Later refinements on this system have tied the negative points to Constitution, applied damage beyond hit points to ability scores more generally (for example Errant RPG), or effectively scored random critical hits with each blow received at zero or less (for example, the many variants on death and dismemberment tables).
In actual play, the last of these gives a nice balance; a zone where characters feel safe, and then a zone where they are at risk of death but still can survive by luck, and get afflicted with really impressive scars, maimings and war wounds. More on the nuts and bolts of that system next post.
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