鼠頭,牛首。

Rat's Head, Ox's Neck.

鼠頭牛首と云ふは、

"Rat's head and ox's neck" means that,

敵と戦のうちに、

when we are fighting with the enemy

互に細かなる所を思ひ合はせて、縺るゝ心になる時、

and both he and we have become occupied with small points in an entangled spirit,

兵法の道をつねに鼠頭牛首、そとうごしゆと思ひて

we must always think of the Way of strategy as being both a rat's head and an ox's neck.

如何にも細かなるうちに

Whenever we have become preoccupied with small detail,

俄に大きなる心にして、

we must suddenly change into a large spirit,

大小にかわる事、

interchanging large with small.

兵法一つの心だて也。

This is one of the essences of strategy.

兵法大分小分にしても、此心を離るべからず。

You must not depart from this spirit in large-scale strategy nor in single combat.

To break the deadlock in a fight where both are preoccupied with details, you should switch between seeing a rat’s head (small & detailed) and seeing an Ox’s neck (big & lacks detail), you should suddenly become lionhearted and asses the situation and be determined to act upon it. You should always keep this in mind whether you fight many in a battle or individuals in a combat. A warrior should apply this even in daily life.