Kim Hee-chul carried out mandatory military service from September 1, 2011 to August 30, 2013. He served as a public service worker for 23 months after undergoing four weeks of basic training at the Nonsan military camp in Chungcheongnam-do. At the time that he enlisted, he had been appearing on KBS's "Secret" (시크릿) as well as the "Radio Star", for which bandmate Kyuhyun took over the role.