Chapter 4 observes the development of soju in Korea during the Chosŏn period, which is characterized by its localization with regard to methods and culture. This period is important to the history of soju, because the spirit spread rapidly throughout Korea and settled into its role as an important Korean alcohol, along with other kinds of alcoholic beverage that had been consumed since antiquity. Soju evolved, leading to its documentation in a variety of sources, including cookbooks that provided households with recipes using soju, medical books containing guides for medical applications of soju, and official documents testifying to the governmental use of soju in domestic and diplomatic gift-giving, an important political activity in premodern government. Soju continued to spread as well: from Korea, the spirit traveled to countries like Japan, as either a diplomatic gift or a trade commodity, creating the opportunity for its transformation into a local Japanese beverage still popular today.