O
Obscurement
Obstacles, in generating a battlefield
on the battlefield
Offensive disarm
Oil
One or two-handed weapons
One-handed weapons used twohanded
One-handedweapon style specialization
Open-faced helm
Opposed rolls
Optional AD&D rules
Oriental weapons
Outside as a battlefield
Outside attack in dueling
Overbearing
a mounted character
during overruns
Overruns
with chariots
with wagons