知彼知己，百战不殆

knowing the enemy and yourself will get you unscathed through a hundred battles (idiom, from Sunzi's "The Art of War")

to know / to be aware

that / those / (one) another

to know the enemy and know oneself (idiom, from Sunzi's "The Art of War")

to know oneself / to be intimate or close / intimate friend

self / oneself / sixth of the ten Heavenly Stems 十天干[shi2 tian1 gan1] / sixth in order / letter "F" or Roman "VI" in list "A, B, C", or "I, II, III" etc / hexa

hundred / numerous / all kinds of

to fight / fight / war / battle

no; not so / (bound form) not; un-

to come unscathed through a hundred battles (idiom, from Sunzi's "The Art of War" 孫子兵法|孙子兵法[Sun1 zi3 Bing1 fa3]); to win every fight

dangerous / perilous / to endanger / almost / probably / only