In a Knights & Knaves Alehouse thread, Stonegiant wrote:
"It is also quite easy to see where [the Eldritch Wizardry alternate initiative] system [for OD&D] gave birth to the initiative system in the Holmes' Edition"
In response I wrote:
Holmes was certainly aware of this system, but determining sources for
his initiative system is difficult. OD&D lacks initiative except for
a statement that Dex determines "speed with actions such as firing
first, getting off a spell", and Holmes includes a revised version of
this that adds "strike the first blow". But the OD&D statement could
be interpreted as either using Dex scores directly, or just a Dex
initiative modifier (which is what Gygax actually suggests in the FAQ in
Strategic Review). The Warlock Supplement (1975), which Holmes used
extensively when he started playing, seems to be the first to explicitly
suggest comparing Dex scores for order of spell casting. Eldritch
Wizardry (1976) uses adjusted dexterity but only for actions other than
melee or movement. Metamorphosis Alpha (1976) uses Dex scores to
determine order of all actions in combat (missile or melee). I think
Holmes was aware of all of these and synthesized them into his own form.
The Holmes rulebook doesn't go strictly by Dex each round, instead
using Dex separately in each "phase" of combat, using the same order of
phases as Warlock (Spell, Missile, Melee).
The Influence of Warlock on Holmes Basic Combat, Part I