Sūnzǐ shuō，jì yào liǎojiě zìjǐ，yòu yào liǎojiě díren，hái yào liǎojiě dìxíng 孙子 说， 既要 了解 自己， 又要 了解 敌人， 还要 了解 地形。 Sun Tzu said you need to know yourself, know your enemy, and know the terrain too. Because in a war, you win by using the environment around you. For example, in World War II, German U-boats won three big battles in the Mediterranean—they hid their boats using the sea’s special water conditions, and that helped them win. So knowing the terrain is really important. For more learning ,welcome to book <The Art of War>~