Over the years I've settled on a way to run 0e/OD&D/White Box combat
that keeps the action moving and is pretty simple, while covering
many cases that come up. I use this basic system for other games
also, maybe with some of the details changed (like weapon damage or
rate of fire in B/X-style games), but the core system remains the
same.

## Surprise

If surprise is in question, I use the standard d6 roll per side,
with 1-2 meaning that side is surprised. Opponents get a free attack
in that case.

## Initiative

I use side-based initiative, with a tied roll meaning simultaneous
action, but with the caveat that the initiative roll is modified by
DEX in the event of a tie. So a PC with a low DEX (8 or less) would
go last on a tied roll, while PCs with an above-average DEX (13 or
more) will go first in that case. I re-roll initiative each round.

## Missiles

I allow two bow shots per round for stationary archers, one if they
choose to move and then fire (or vice versa). Elves can always fire
two shots, however, even if moving.

Shooting into melee is at -4 to the attack roll, with no range
bonuses allowed. On a natural 1, an ally is hit, determined
randomly.

Other missile weapons can be fired once per round, except for
crossbows, which can be fired every other round.

## Melee

Combatants can choose whom they want to attack. Attacks from behind
are at +2, except for thieves, who get +4 when unnoticed.

Moving in combat is at 1/3 of the base movement rate times 10, so a
leather-armored PC with a base move of 12 can move 40 feet per
combat round. Leaving combat can be done slowly with a fighting
retreat without penalty - but the opponent can always
follow. Fleeing combat outright gives opponents a free attack at +2.

Charging into combat with initiative will give the attacker +2 to
their attack roll, but if they miss, their opponent gains +2 on the
return attack.

Spears and pole arms can attack from the second rank as thrusting
weapons, and spears do an extra point of damage when used
two-handed.

Position can be important, for example if three PCs are attacking an
Orc, and the Orc is using a shield, one of the PCs will be attacking
the shieldless flank.

Sometimes PCs want to switch weapons in the same round, like from
bow to sword at the start of combat. I allow this, as long as the
weapon in hand is dropped. Otherwise, it takes a full round to stow
the first weapon and ready the second.

## Crits & Fumbles

I don't like detailed critical hit/fumble tables [0]. I keep it
simple - a natural 20 always hits (barring magic or silver required)
and does maximum damage, while a roll of 1 is an automatic miss (but
see above for shooting missiles into melee).

## Death and Wounds

Binding wounds can be done after any combat and will heal 1d3 hp.

PCs die at 0hp or less, however they do get a save versus death in
that case, adding any CON bonus/penalty to the roll. If they
succeed, they are left with 1hp and cannot regain any hit points
that day without the use of magic, nor do they get a second chance
if they fall to 0hp again.

## Spells

Spells can be prepared and held in that state until cast. Prepared
spells go off before any melee or movement actions for that PC's
side. Otherwise, any spell takes one combat round to prepare (scroll
spells go off first the round after the scroll is dug out of a pack
or pouch and opened). If it is important to know if one spell goes
off before another on the side that wins initiative, I compare DEX
scores of the spellcasters.

I assume that keeping a spell prepared does take some small level of
concentration, so if a spellcaster is hit by an attack, any prepared
spells are lost (but can be re-prepared starting the next round in
that case, they are not lost from memory). It is not possible to
prepare or cast a spell from memory while in combat, but spells cast
from magic items can be used in combat.

## Gaze Attacks, Magic Items and Breath Weapons

Gaze attacks always take effect first, followed by spells cast from
magic items (like wands, rings or staves) and breath weapons, which
will both take effect before melee or movement, but simultaneous
with prepared spells. So all told, this is the order of actions per
side:

- Gaze attacks
- Prepared spells, spells cast from  magic items, breath weapons
- Missile fire, melee & movement

I don't care whether movement takes place before or after an attack,
or when missiles are fired. For a given side, I'll just go around
the table (or VTT) and combatants will act in order. Depending on
circumstances, I let players hold their PC's action, so for example
they can charge in to attack just after their companion fires a bow.

[0]: gopher://gopher.smolderingwizard.com/0/phlog/2021-03-04-critical-hits-fumbles.md