Surprise

Master Waller values pragmatism and simplicity above all else, so the response to assault is very sudden and efficient.
Invariably the attacker is surprised to find themselves on the floor, or struck.
They have no idea how we countered them.

Taking the initiative is paramount in self defence.
If the attacker abruptly experiences a 'reversal' - going from attacker to victim - this is a difficult adjustment to cope with.
It gives them pause for thought.