Bare-handed combat

Combat Skill

Gives bonus to-hit and to-damage when no weapon is wielded. Can be used with weapon gauntlets.

You do not have to reach Grand Master level here before enhancing martial arts; that only needs enough training and free skill slots. What Grand Master level changes is the training: kicks train martial arts at any time, but unarmed hits train bare-handed combat until your effective level in it reaches Grand Master, and only then train martial arts instead (or nothing, if your role cannot learn martial arts). A worn headband of martial prowess adds two levels to your effective level, so while you wear it, unarmed hits stop training bare-handed combat once the skill is Expert or better.