How did the National Revolutionary Army prepare itself in the face of the full-scale outbreak of the Sino-Japanese War? What were Chiang Kai-shek’s military plans? These issues have long occupied scholars. This article seeks a new path that leads to new discoveries by closely examining the endeavors of the military’s staff organization at the highest levels. Among the Great Powers, from the nineteenth century onwards, the highest levels of military staff gradually became the core of their top level military organizations. The general staff provided information, drafted detailed military plans, transferred military orders, and oversaw how the commander executed war plans. The same organization could also be found in late Qing China when the empire undertook military reforms in imitation of the Western and Japanese systems. In Republican China, this organization came to be named “General Staff Headquarters.” In early Republican years, military institutions were still embryonic; therefore, the General Staff did not exert significant functions until it was reorganized after the Northern Expedition. While Chiang Kai-shek was often known by his post as Chairman of the Military Affairs Commission, few remember that Chiang concurrently held the post of Chief of Staff for a long time in order to supervise the planning and drafting of national defense strategies against the Japanese forces. This study examines the national defense plans made by the General Staff Headquarters. It tries to answer the following questions: Who made the plans? How? What were they? What were the relations between these plans? How did plans develop over time? Was there any intention to draw the enemy southward or divert the Japanese army’s operational line? Lastly, this study discusses the execution of the plans when the Sino-Japanese War broke out. It finds that in contrast to low level staff units, who tended to be ignored, the General Staff Headquarters was able to inspect key strongholds nationwide under the suggestions of German military advisors and drew up plans on all levels. These plans did not merely exist on paper. They were able to foresee the deployments of Japanese armies and were effectively executed in the early stages of the war. The Battle of Shanghai was pre-planned without strategic intention to draw the enemy southwards. To strengthen Southwestern strongholds in preparation of the National Revolutionary Army’s retreat was also stated in plans, while the areas in northern China, along river banks, and on seacoasts were not intended to be abandoned easily. Apart from drawing up well-known plans such as mobile warfare and guerilla warfare over large spaces, the General Staff also laid emphasis on strategic techniques such as active defense, decisive battle, counter-offensive, and large-scale trench warfare.