Idea for speeding up D&D combat

Still here 

So Silent Titans fell through for me. Love the book, but I had a hard time running it. I took a break, spent some time as a player in a 5E game, and I've just kicked off a new campaign into Stonehell. I expect this to be more comfortable territory for me. The first campaign I ran for my gaming group was a megadungeon. I really like the focus they provide. This is the game space. This is where the game takes place. Let's go there and play.

Anyway

Old School Essentials got me pumped to run old school Dungeons & Dragons again. I was mostly running Into the Odd for a while. One thing I'm going to miss from ItO is the speed of combat. It's quick, it's dangerous, and it puts the players right to the interesting decision points. And I love how even though players can recover some damage after a fight, they are still getting slowly ground towards death by lowering ability scores. How can we make old school D&D combat more like that? Here's a house rule I've been theorizing.

Hits and hit points 

The basic idea is taking the pool of Hit Dice and splitting it between Hit Points (normal HP we all know and love) and "Hits" (the number of additional hits the character can survive)

• When rolling a character or monster's hit dice:
• Roll the first die normally, add CON modifier, add any other modifiers, etc, result is their "Hit Points"
• Don't roll any of the remaining dice. The number of remaining dice is their "Hits"
• When a character levels up, they gain another Hit. They do not gain any more HP.
• Might give additional Hits on level up for high CON
• CON 13-15: Additional Hit at level 4, 8, 12, etc.
• CON 16-17: Additional Hit at level 3, 6, 9, etc.
• CON 18: Additional Hit at level 2, 4, 6, etc.
• Maybe let them re-roll their single Hit Points die at level-up and keep the new score if higher?

An example: The party encounters a 7 HD Cave Bear. Roll a single d8 (the usual size for a monster). Result is a 5. The bear has 5 HP. There are 6 hit dice remaining, so the bear also has 6 Hits.

5 HP, 6 Hits

Combat 

• During combat, roll to-hit as normal. If the attack is successful...
• ...and the target has any Hits remaining, they lose one Hit
• ...and the target has only Hit Points remaining (no Hits), roll damage and reduce HP as normal
• Death or incapacitation at zero HP
• For attacks that normally roll multiple dice for damage, e.g. our Cave Bear's 2d6 bite attack:
• Consider treating it as separate successful attacks of that die size.
• Reduce Hits first.
• If Hits are at zero, each remaining die is rolled against HP.
• Any pluses on damage are only applied when rolling against HP, and are only applied once.

Healing 

• Once per hour, characters can take a 1 turn rest, drink some water, and recover 1 Hit
• They cannot recover HP this way, only Hits
• Fits well with the B/X expectation that the party is already resting once every hour or after every combat.
• Each full day of rest back in civilization:
• Recover 1 HP
• Recover 1d3 Hits
• Magical healing would work like the reverse of attacks that do multiple dice of damage.
• Treat each die of healing separately.
• Roll the die and recover HP first.
• If HP is at max, each remaining die of healing recovers one Hit.

Theorizing 

The inspiration for this comes from a couple sources. First, Chris McDowall's post on how he would make D&D combat more like Into the Odd.

http://www.bastionland.com/2018/10/d-combat-supercharger.html

Secondly, my probably incorrect understanding of the history of Hit Points in Dungeons & Dragons. It goes:

"In the beginning, there was Chainmail. You rolled dice and consulted attack matrices to determine whether your soldiers hit their soldiers. You did not roll damage. You simply did one "hit" of damage on each successful attack. And figures could only take 1 hit before they died. Number of hits meted out or able to be sustained did increase for more powerful figures, but basically 1 successful attack = 1 hit = 1 dead figure.

Dave Arneson starts using Chainmail to resolve combat in his proto-D&D game. Level 1 characters are equivalent to basic Chainmail troops. One hit and they die. Turns out in a game where you only control a single figure, always dying to a single hit isn't much fun. So they decide to turn Hits into Hit Dice that are rolled to determine Hit Points. And when damage is dealt, a similar die roll is made to determine how many Hit Points are lost. You now have a slim chance to survive multiple hits, even if you only have one Hit Die. (Although, on average, you will still die in one hit, Hit Dice and Damage Dice being mirrored the way they are.)"

And that was more fun. Until things get slowed down by HP bloat. Or you have to deal with the disappointment of miraculously hitting the dragon but rolling a 1 for your damage.

So let's make a bold assumption: The benefit of using Hit Points and Damage Rolls instead of Hits is only important when you can survive only one Hit.

It's that chance that maybe you'll get lucky and be able to survive that last, fatal attack. If there's no chance that the current damage will kill you, rolling and determining exact HP and damage is less important. Just take and lose 1 Hit. It's quicker. On the long average, the result is the same. Rolling a 1 for damage is way more annoying when the enemy has 37 HP left than when they have 3 HP left. One is boring and feels like nothing changed. The other is "Damn, so close!"

The ability to recover Hits but not HP via short rest is my attempt to replicate the "recovered slightly, but still grinding closer towards death" feel from Into the Odd.

How it will work out in practice? I don't know yet. I don't even know if this will find its way into my campaign or if I'll just run it traditionally. Any thoughts or suggestions?