[知彼知己,百战不殆 / 知彼知己,百戰不殆, zhī bǐ zhī jǐ, bǎi zhàn bù dàiㄓ ㄅㄧˇ ㄓ ㄐㄧˇ, ㄅㄞˇ ㄓㄢˋ ㄅㄨˋ ㄉㄞˋ] Knowing the enemy and yourself will get you unscathed through a hundred battles (成语 saw, from Sunzi's Art of War).
[あらゆ(新湯);さらゆ;しんゆ(新湯), arayu ( shin yu ); sarayu ; shinyu ( shin yu )] (n) clean, freshly poured bath; hot water just poured into a bath that no one has entered yet
[かれをしりおのれをしればひゃくせんあやうからず, karewoshirionorewoshirebahyakusen'ayaukarazu] (exp) If you know your enemy and know yourself, in a hundred battles you will never be defeated.