The Four Commanderies of Han (Korean: ; Hanja: ) were Chinese commanderies located in northern Korean Peninsula and part of the Liaodong Peninsula from around the end of the second century BC through the early 4th AD, for the longest lasting. The commanderies were set up to control the populace in the former Gojoseon area as far south as the Han River, with a core area at Lelang near present-day Pyongyang by Emperor Wu of the Han dynasty in early 2nd century BC after his conquest of Wiman Joseon. As such, these commanderies are seen as Chinese colonies by some scholars. Though disputed by North Korean scholars, Western sources generally describe the Lelang Commandery as existing within the Korean peninsula, and extend the rule of the four commanderies as far south as the Han River. However, South Korean scholars assumed its administrative areas to Pyongan and Hwanghae provinces.
Three of the commanderies fell or retreated westward within a few decades, but the Lelang commandery remained as a center of cultural and economic exchange with successive Chinese dynasties for four centuries. As its administrative center in Lelang, the Chinese built what was in essence a Chinese city where the governor, officials, and merchants, and Chinese colonists lived. Their administration had considerable impact on the life of the native population and ultimately the very fabric of Gojoseon society became eroded.Goguryeo, a later founded, a mixed Koreanic and Yemaek kingdom, slowly began conquering the commanderies and eventually absorbed them into its own territory.
A commandery that was separated out of Lelang Commandery in the later years of its history is the Daifang Commandery (, , AD 204 ~ AD 313)
In the North Korean academic community and some parts of the South Korean academic community, the Han dynasty's annexation of the Korean peninsula have been denied. Proponents of this revisionist theory claim that the Han Commanderies actually existed outside of the Korean peninsula, and place them somewhere in Liaodong Commandery, China instead.
The demonization of Japanese historical and archaeological findings in Korea as imperialist forgeries owes in part to those scholars' discovery of the Lelang Commandery—by which the Han dynasty administered territory near Pyongyang—and insistence that this Chinese commandery had a major impact on the development of Korean civilization. Until the North Korean challenge, it was universally accepted that Lelang was a commandery established by Emperor Wu of Han after he defeated Gojoseon in 108 BCE. To deal with the Han Dynasty tombs, North Korean scholars have reinterpreted them as the remains of Gojoseon or Goguryeo. For those artifacts that bear undeniable similarities to those found in Han China, they propose that they were introduced through trade and international contact, or were forgeries, and "should not by any means be construed as a basis to deny the Korean characteristics of the artifacts". The North Koreans also say that there were two Lelangs, and that the Han actually administered a Lelang on the Liao River on the Liaodong peninsula, while Pyongyang was an "independent Korean state" of Lelang, which existed between the 2nd century BCE until the 3rd century CE. The traditional view of Lelang, according to them, was expanded by Chinese chauvinists and Japanese imperialists.
While promoted by the academic community of North Korea, and supported by certain writers and historians in South Korea, this theory is not recognized in the mainstream academic circles of South Korea, the United States, China (and Taiwan) and Japan.
Korea in 108 BC. Wiman Joseon before destroyed by Han dynasty
Korea in 315. Goguryeo recovered the former Gojoseon territory.