As I was reading "The Unfettered Mind" by Takuan Soho, I noticed that the author makes an analogy between a sword parry and a Zen koan. Here are some relevant bits from "The Mysterious Record Of Immovable Wisdom":
if the mind stops with the sword with which a man is going to strike you, there
will be an interval, and your own action will be lost.
But if in the interval between your opponent's striking sword and your own action
you cannot introduce even the breadth of a hair, your opponent's sword should become your own.
In Zen, if asked, "What is the Buddha?" one should raise a clenched fist.
If asked, "What is the ultimate meaning of the Buddhist Law?" before the words
have died away, one should respond, "A single branch of the flowering plum" or
"The cypress in the garden".
It is not a matter of selecting an answer either good or bad. We respect the mind
that does not stop. The non-stopping mind is moved by neither color nor smell.