South Korea’s security discourse on the nuclear threat posed by North Korea has been dichotomised by its position within the political spectrum between the progressives and conservatives. By drawing upon Securitisation Theory (ST), this study challenges the current security discourse in South Korea, which has divided and misled the public as well as securitising actors. This study examines the security discourses of the Roh Moo-hyun (2003–2008) and Lee Myung-bak (2008–2013) administrations, since they represent the archetypes of the progressives and conservatives respectively. The results of the analysis suggest that the current security discourses that have been prevalent in South Korea do not correspond with reality and, subsequently, the discourses were not able to deal with real challenges that the nuclear threat posed. This research also explains the root cause of the distorted security discourses by applying a ‘discursive chasm’ as a preliminary concept, which indicates a discursive structure that fundamentally impedes the performance of securitising actors’ articulation, and that distorts the discursive formation (securitisation processes). The chasms consist of three elusive discourses: first, a discourse on threats that cannot simply be said to be either imminent or not imminent (nuclear weapons as materiality and discourse); second, a discourse on the other that cannot easily be defined (the difficulty of representation of North Korea); and third, a discourse on measures that cannot easily be realised (intangible extraordinary measures).

South Korea’s security discourse on the nuclear threat posed by North Korea has been dichotomised by its position within the political spectrum between the progressives and conservatives. By drawing upon Securitisation Theory (ST), this study challenges the current security discourse in South Korea, which has divided and misled the public as well as securitising actors. This study examines the security discourses of the Roh Moo-hyun (2003–2008) and Lee Myung-bak (2008–2013) administrations, since they represent the archetypes of the progressives and conservatives respectively. The results of the analysis suggest that the current security discourses that have been prevalent in South Korea do not correspond with reality and, subsequently, the discourses were not able to deal with real challenges that the nuclear threat posed. This research also explains the root cause of the distorted security discourses by applying a ‘discursive chasm’ as a preliminary concept, which indicates a discursive structure that fundamentally impedes the performance of securitising actors’ articulation, and that distorts the discursive formation (securitisation processes). The chasms consist of three elusive discourses: first, a discourse on threats that cannot simply be said to be either imminent or not imminent (nuclear weapons as materiality and discourse); second, a discourse on the other that cannot easily be defined (the difficulty of representation of North Korea); and third, a discourse on measures that cannot easily be realised (intangible extraordinary measures).