Excerpt from <span class="chinese-post-title">虛實</span> Attack by Stratagem in <span class="chinese-post-title">兵法</span>The Art of War

知彼知己，百戰不殆；不知彼而知己，一勝一負；不知彼，不知己，每戰必敗。

孫子

"If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle."

Unless noted otherwise, all quotations of classical texts and accompanying translations come from the Chinese Text Project