Who said "When they start to crack, don't let the moment slip."?

Miyamoto Musashi (c. 1584–1645). Source: The Book of Five Rings, Fire (Knowing Collapse).

What is the original Japanese?

敵のくづるゝ拍子を得て、其間をぬかさぬ樣に追たつる事肝要也. Translated from the original Japanese by Spartan Surfers.

When they start to crack, don't let the moment slip.

Miyamoto Musashi, The Book of Five Rings, Fire (Knowing Collapse)

The source

"When they start to crack, don't let the moment slip." Miyamoto Musashi said it in The Book of Five Rings, Fire (Knowing Collapse). Translated from the original Japanese by Spartan Surfers.

"敵のくづるゝ拍子を得て、其間をぬかさぬ樣に追たつる事肝要也"

Original Japanese, The Book of Five Rings, Fire (Knowing Collapse). Japanese: Miyamoto Musashi (Kinkodo, 1909), NDL digital text.

Who said it

Miyamoto Musashi (c. 1584–1645). Undefeated swordsman who wrote The Book of Five Rings in a cave a few weeks before he died.

Questions

Who said "When they start to crack, don't let the moment slip."?: Miyamoto Musashi (c. 1584–1645). Source: The Book of Five Rings, Fire (Knowing Collapse).
What is the original Japanese?: 敵のくづるゝ拍子を得て、其間をぬかさぬ樣に追たつる事肝要也. Translated from the original Japanese by Spartan Surfers.