B/X Morale for AD&D

 I posted these rules in a reddit comment a while back, but I figured I'd post it again here to make it easier to find.

So, Basic D&D has a 2d6-based morale system, where each individual monster is given a score from 2 to 12.

Page 67 of the AD&D DMG, on the other hand, presents a d100-based morale system. There is a base score of 50%, plus 5% per hit die, plus 1% per hit point above the die. Then, if a morale check is failed, the margin of failure is checked against a table, which I've duplicated below.

1% to 15%	fall back, fighting
16% to 30%	disengage-retreat
31% to 50%	flee in panic
51% or greater	surrender

It's also worth noting that AD&D requires morale checks more frequently. A check is made each round when faced by an obviously superior force, when 25% of the party is killed, when 50% of the party is killed, when the leader is unconscious, and when the leader is slain; whereas B/X only requires a morale check upon the first kill, and when half the party is killed.

Now, the difference in systems creates a problem. I, and I think most of us, prefer the B/X morale system—but AD&D monsters don't have morale ratings, and B/X provides no way to calculate morale based on the monster's other stats.

So I set up a spreadsheet and mapped the AD&D rules onto a 2d6 roll. In practice, the extra 1% per hit point winds up being essentially negligible, so the end result is a simple table by hit dice:

HD	Morale
0-1	6
2-4	7
5-8	8
9+	10

It's interesting that these categories actually map very well onto the "Normal Man"/"Hero"/"Superhero" categorization that we see in OD&D and Chainmail. Probably just a coincidence, but it's nice that we get some memorable breakpoints on the table.

These values do tend to be a little bit lower than B/X, even if you use the B/X rules that have monsters making fewer morale checks. Vonsidering that a failure of 15% or less is only "fall back, fighting" in AD&D, whereas B/X doesn't bother with different degrees of failure, I don't think it's entirely unreasonable to add +1 to all of these values in order to bring the two systems more in line with each other. (Adding 15% to the underlying percentages is also an option, and roughly similar in the end, but I've decided not to go with that option since it leads to an uglier and less memorable table in my opinion.)

Increasing the values by 1 also gives a maximum value of 11—the highest non-guaranteed value in the B/X system—which also nicely approximates the way things tend to work out in AD&D, where high-level monsters are guaranteed or near-guaranteed to succeed their morale checks.

So finally we get this table:

HD	Morale
0-1	7
2-4	8
5-8	9
9+	11