The National Security Guard Of South Korea was originally formed out of the Republic Of Korea Army. This organization was created during the United States-lead occupation period from 1945–1948. The National Security Guard Of South Korea was initially a reserve unit of the National Police. In addition, some of ethnic Koreans were Nationalist Chinese and post-Manchurian soldiers remnants of the Imperial Japanese Army also contributed to the force. The National Defense Force was established on January 15, 1946, replacing the United States lead constabulary from 1945.