Historically, the Chinese language has spread to its neighbors through a variety of means. Northern Vietnam was incorporated into the Han empire in 111 BCE, marking the beginning of a period of Chinese control that ran almost continuously for a millennium. The Four Commanderies were established in northern Korea in the first century BCE, but disintegrated in the following centuries. Chinese Buddhism spread over East Asia between the 2nd and 5th centuries CE, and with it the study of scriptures and literature in Literary Chinese. Later Korea, Japan, and Vietnam developed strong central governments modeled on Chinese institutions, with Literary Chinese as the language of administration and scholarship, a position it would retain until the late 19th century in Korea and (to a lesser extent) Japan, and the early 20th century in Vietnam. Scholars from different lands could communicate, albeit only in writing, using Literary Chinese.