Proto-D&D Rules Speculation: Damage Mitigation

In my research on how early Blackmoor combat worked, I have been digging in a number of forum threads on the ODD74 forum. One of the threads, entitled "Blackmoor Combat and Arnesons System" had a post by Dan Boggs (Aldarron) that stimulated my curiosity. In this post, he posted the details of a conversation that he had with original Blackmoor player, John Snider. Snider recounts how damage mitigation works (to the best of his memory):

Dan:
If the “to hit” matrix was level vs level then the Armor Class may have functioned as a saving throw – perhaps the 2d6 system mentioned above.

Mr. Snider
Saving ... I remember that this was a mitigator on how bad the hit hurt or how much damage you inflicted. Yes, armor and (if rem right) agility (or whatever we called it back there) were both mitigators, as was level. Boy I wish I had my papers from back then .. then I'd be able to help you a heck of a lot more. I'll look in the archives down below but am sure don't have them anymore.

Dan:
So, if I’m reading it right, you’re saying the mitigating factors came after a hit was already determined, in other words you think you remember 2d6 being rolled to determine if a hit was successful; so Dave first checked what you rolled against something he had written down to determine if a hit was made, before Armor Class etc. came in to play? Then, Armor Class, Agility, and level were mitigators on damage received and damage done after a hit had already been determined. Correct?

Mr. Snider:
Again what I recall at first, although it might have changed as the game matured, I believe Agility was used by Dave before the roll. AC was (if recall) applied after to mitigate the damage ... this also might have changed during the 1st year or so of game maturation. Level, was used by, I can't recall how at this point .. sorry.

Dan:
Was the level mitigator perhaps a separate kind of progression like getting more dice to attack with, say 4d6?

Mr. Snider
I can't recall how level played in although I know it did, just can't recall after all that time.

See: Dan Boggs Conversation with John Snider

Before reading this, I was completely unaware of an Agility trait being used in Blackmoor (for more info on what is known about character traits see my wiki article Character Traits And Mechanics). Looking at David Megarry's character sheets there are red numbers which seem unaccounted for (which you can see in this image running across the top of the page). Those numbers range 0-7, which if that is the actual range would be within a 1d6-1 to a 1d6+1 range. After thinking about this for a bit I remembered from Arneson's First Fantasy Campaign Introduction he wrote, albeit a short section, about damage mitigation:

"As the player progressed he did not receive additional Hit Points, but rather he became harder to Hit. All normal attacks were carried out in the usual fashion but the player received a "Saving Throw" against any Hit that he received. Thus, although he might be "Hit" several times during a melee round, in actuality he might not take any damage at all. Only Fighters gained advantages in these melee Saving Throws."

Arneson, Dave. First Fantasy Campaign, Judges Guild, 1980.

There seems to be two concepts here - a) being harder to hit, and b) the possibility of not taking any damage at all. Lets tackle the first (the second one we can save for another post). Being harder to hit would, at least to me, imply not being touched by your opponents weapon. If the number in the red circles are actually the Agility trait that John Snider referred to, it would work like all the other known Character Traits. Arneson seems to imply that players became harder to hit as they progressed in levels. If they are harder to hit, that would mean that the damage mitigator would increase to be easier to roll as players progressed. How would that look? In practice we could use a basic formula:

AGILITY + PLAYER LEVEL = DAMAGE MITIGATION TARGET

In Blackmoor, Fighter progression seemed to originally be based on a 3-level system (according to Greg Svenson):

"My recollection is that a flunky or man-at-arms rolled 1d6, a hero rolled 4d6 and a superhero rolled 8d6 for damage. Warriors only had three levels in the days before D&D was published. I think that Dave just told us how many hit points of damage we could take."

So that level sequence would look like this:
Level 1: Flunky
Level 2: Hero
Level 3: Superhero

So it is possible that initially the maximum damage mitigation target number was 10. Later levelling for a Fighter changed to a new hit die per level (according to Greg Svenson):

"We had a player (Bill Heaton) advance a level in the very first adventure. There were only three levels at the time: flunky, hero and super hero. We were all flunkies at the start. He became a hero when he mastered the magic sword we found during the adventure. I don't remember when the level advancement became one level per new hit dice and we were never really sure how far along we were in getting to the next level, Dave kept track of our experience and let us know when we moved up."

With the change to a more standard levelling approach that we would recognize from OD&D, players could level up indefinitely, and the Agility damage mitigation would not be capped. But Greg might be remembering playing early OD&D.

So how would this mechanic work? While I can only speculate, here is how I would reconstruct it: "On successful hit, the defending player would roll 2d6-2. If the roll was under the target number, the player mitigated being hit." The 2d6-2 range is between 0 and 10.

Agility to me, rings of speed and lightness of foot. Someone with great Agility would be able to bolt out of the way of an attack, especially if they are well trained at it. That would make it difficult to hit, but would get easier with level. Also Arneson was fond of rolling under a target value. It's a rather simplistic system if that is how it was actually implemented.

I propose this Combat Procedure for Blackmoor:
Note: Players go first, but if they delayed too long monsters go first.

1. To Hit: Roll a melee saving throw under the listed weapon value on the character sheet plus Combat Modifier.
2. Damage Mitigation: 
1. John Snider suggested an Agility roll for damage mitigation.
2. Players and some monsters with Armor listed can roll an Armor Savings Throw over their Armor value.
3. Damage: Roll 1 six sided die for each Hit Die of the level the character has achieved minus Magic Armor rating.

See Combat on my Rules Wiki

Later in 1979, Dave Arneson would publish his own rule system with Richard Snider (Johns brother). In Adventures in Fantasy we are given a mechanic for modifying the hit chance based on dexterity of two combatants:

(Higher Dexterity - Lower Dexterity) / 2 = Basic Factor %

The Basic Factor % is added/subtracted from the two Combatants Hit Chance calculations. While not the same as I propose for early Blackmoor, it does show an evolution of the concept into a more formula based approach which Arneson and Snider were both known (and criticized) for, which we see in Adventures in Fantasy for many of the classic systems Arneson created.