The prevailing belief is that the ACS included in OD&D replaces Chainmail.
What is missed is that the "normal" combat system in Chainmail is its Mass Combat, while the derived systems are given clear titles like "Man to Man".🧵

https://twitter.com/AlchemicRaker/status/1983357449890312470

Chainmail begins by launching into its "normal" / core combat system, which is what we tend to qualify as "mass combat". While it never receives a name, we can recognize it by certain cues, such as referring to 1:20 or 1:10 figure scale combats.

The Old Lords is a clone of Chainmail (as far as OD&D is concerned) with superior layout and 2-page spreads, including clarifications for use with OD&D!
Physical copies are now once again available at DTRPG!
And as always, the PDF is FREE! (see the Description on the store page) The PDF and Softcover copies are available on DTRPG!
drivethrurpg.com/en/product/483…

Braunstein has a unique place, but can't stand alone as the lifeblood of a campaign. You need the crossover. Adventure Sessions (exploration game loops), a Domain Game (which is where patron play fits, or Diplomacy in Gygax's day), a Wargame (heroic or mass battles), or Braunstein (RP-focused; but only matters because of the outcomes it has in the other 3 game modes) The original Braunstein worked as well as it did because the players were mislead about the importance of the play session.
The Godstein works (creation + ongoing divine council) because it has such notable effects on the game world.
Same for the Bros' Brovenloft, etc.

From my studies examining the #ADnD, RAW, it pushes not only for 1:1 downtime, but ALSO for 1:1 play within sessions of play as well. The evidence is in the 1e DMG, and also appears directly referenced, and similarly implied, in modules made during that time.

In the 1e DMG, 1979:
1:1 between sessions is recommended
Combat rules heavily imply 1:1/real-time as well, with 1 minute combat rounds, and if a player dithers for what to do on their turn for a whole minute, to skip their turn, as they are representative of their characters' inability to decide as well
Combat rules also describe that whatever players are discussing at the table during combat, can be heard by the local NPCs as well

In the Tomb of Horrors, 1978:
instructed to assume 1:1 time between sessions, to recover adventurer HP
1:1/real-time events, such as counting down from 10 as a door seals shut, are described

Throughout #ADnD, the design is to keep the decision space most closely in sync between the players and their characters, and how players decide to use their own time contributes to their success or detriment. In other words, immersion in time. "it is best to use 1 actual day = 1 game day"
#ADnD DMG, page 37