4·19 혁명
At the outset of the Korean War in 1950, Ahn was released from prison, having served only one year of his 15-year sentence. Upon his release, Ahn was re-instated as a military officer. After serving under Rhee during the Korean War, Ahn was discharged in 1953, having attained the rank of colonel. After Syngman Rhee fled Korea in response to the April Revolution of 1960, Ahn went into hiding, living under an assumed name.