Four Commanderies of Han

The Four Commanderies of Han (漢四郡, 한사군) are Lelang, Lintun, Xuantu and Zhenfan commanderies in northern Korean Peninsula and part of the Liaodong Peninsula. set up by Emperor Wu of the Han dynasty in early 2nd century BC after his conquest of Wiman Joseon. The commanderies were set up to control the populace in the area as far south as the Han River, with a core area at Lelang near present-day P'yongyang, which was previously under the control of Gojoseon. The accurate positions of the commanderies other than Lelang commandery are still under debate.

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 ultimatedly 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.