彼を知り己を知れば、百戦殆からず（かれをしりおのれをしれば、ひゃくせんあやうからず）

Japanese vocabulary

Meaning: if you know your enemy and know yourself, in a hundred battles you will never be defeated; know your enemy

See it used in real works

• Example sentences from Japanese novels & web fiction (Massif)
• Hear “彼を知り己を知れば、百戦殆からず” pronounced in real videos (YouGlish)