The void related to kiai

Questions ask by Darrell Max Craig to Harutane Chiba sensei in the book 'The heart of Kendo':

CRAIG: Sensei, I find it hard to make a student understand the kiai's importance.
SENSEI: That's only natural. Most people think it comes from the brain, but in truth, if it is properly executed, it comes from the inner strenght of the stomach. This is called tanden in Japanese. The proper kiai can appear only if the mind is not activated to make improper movements of the body. The mind must be in a complete state of muga.
CRAIG: What is muga?
SENSEI: Here again is one of those Japanese words that has many definitions and is extremely hard to translate. I feel it is best explained by saying the mind is in a state of complete void or emptiness, a state of no ego... Are you following me, Craig Sensei?
CRAIG: Yes, I think so. You're saying when your practice becomes subconscious instead of conscious?
SENSEI: You are on the correct path. This muga is the state of mind all kendoists hope to obtain eventually but seldom do. When a student reaches this level in his practice he has no thought of defeat or victory. He s not afraid of death and there is no anger in his heart, only peace.


Later in the text it says:

[...] I have heard my father talk about samourai who developed such a strong kiai from the lower abdomen it would off-balanced their oponent in combat. A samourai of this stature would split a stalk of rice with a single stroke of his sword or cut down flies in midflight.


Well, I guess we all still have quite a bit of work to improve are kiai!!!