Introduction to the corridor in the courtyard: The first "Plan" discusses how to plan before and during war, and discusses the importance of planning in war. Sun Wu believed that before starting a war, it is necessary to conduct careful research and comparison of the basic conditions of the enemy and ourselves, and to plan carefully in order to formulate a correct battle plan. There are five basic conditions that determine the outcome of a war: "Tao" (morality), "Tian" (timing), "Di" (geographical convenience), "General" (general), and "Fa" (legal system). Once we understand these conditions clearly, we can determine the outcome of the war. During the war, we must also conduct research and planning based on the interests and changing situations, and adopt flexible measures to attack the enemy "unprepared and by surprise." Sun Wu also believed that if you plan carefully, you may win in the war, but if you plan poorly, it will be difficult to win, and if you don't plan at all, you will definitely fail.