In this chapter, we introduce medicine and public health before and during World War II (1945). Furthermore, we will look back on how Japan reached the starting point for building its social security system after World War II. In Japanese history, the period from 1603 to 1868 is known as the Edo period. During this time, the country was ruled by the Tokugawa shogunate, with the central government based in Edo, now Tokyo. The Edo period was marked by approximately 260 years of peace and stability. Economic growth and social order allowed samurai, merchants, and townspeople to pursue education and cultural activities