Under the U.S. military administration, the South Korean National Defense Guards founded on Jan 15th 1946.
On Aug 15th 1948, the Republic of Korea government was finally founded, and on Sep 5th of that year, the National Defense Guards was renamed as the Republic of Korea Army, and became a part of the Republic of Korea Armed Forces.

The ROK Army put an enormous amount of effort in increasing armed forces, and was able to build 6 divisions before the Korean War. During this period, the ROK Army deterred North Korea's continuous and numerous provocations, such as dispatching Communist Guerillas, by swift and effective responses.