元となった辞書の項目
彼を知り己を知れば百戦殆からず
phrase
(literally) know the other side and yourself, a hundred battles will not be perilous
意味（1）
(literally) know the other side and yourself, a hundred battles will not be perilous
意味（2）
(figuratively) it is important to understand the strength and weakness of your side and the opposing side, in order to mitigate the risk of failure
