expression
know your enemy and know yourself, and you will never be defeated in a hundred battles
Proverb from Sun Tzu's The Art of War. Used to emphasize the importance of understanding both one's own strengths and the opponent's situation before engaging in any conflict.
「彼を知り己を知れば、百戦殆からず」という言葉は、ビジネスでもよく引用される。
The saying 'If you know your enemy and know yourself, in a hundred battles you will never be defeated' is often quoted in business as well.
From Sun Tzu's The Art of War (孫子). The Japanese rendering is a classical Chinese-derived expression, using literary grammar and kanji readings.