The ongoing tension between North Korea (NK) and South Korea (SK) has been affected by threats involving a nuclear. In this essay, I will focus on NK- SK relations that have been influenced by two of NK's recent nuclear threats: a cyber attack that delayed functioning of a nuclear energy plant in SK and attempts to divulge plants blue prints, and NK's recent announcement on testing of their hydrogen bomb.
On December 9, 2014, more than 3,500 employees of state-owned Korea Hydro and Nuclear Power of South Korea received emails containing malicious codes.  This cyber attack disrupted its functioning for days, and erased information stored in hard drives.  South Korean prosecutors claimed this attack to have originated from North Korea, based on the fact that composition and working methods were the same as what North Korean hackers used. North Korea's state newspaper denied involvement in this cyberattack, calling such accusations a scheme to escalate tension between North and South Korea. 
On January 6 of this year, North Korea announced that is successfully tested an experimental hydrogen bomb. It was the fourth nuclear test since 2006.  Despite the validity of the announcement, South Korea resumed anti-NK propaganda broadcasts across the border as a result.  The broadcasts include criticism of the North Korea's nuclear test and its leader Kim, dire human rights conditions and economy of NK, as well as K-pop songs (which are prohibited in NK) and general world news.  NK condemned this broadcasts as SK's attempt for psychological warfare, and warned that the continuation of these broadcasts will result in an escalated tension across countries. But provided that NK responded to this broadcast by firing artillery, and that it caused a quasi-state of war in August 2015 that was resolved right before the deadline NK proposed, South Korea's continuation of these loudspeaker broadcasts is likely to cause another dire moments between Koreas. 
As one of the two countries that shares a border with North Korea, South Korea pursued a cautious and firm diplomacy with NK when nuclear threat's involved. The first case of cyber attack was not confirmed to have been executed by North Korea, and no critical piece of information was disclosed since the hackers failed to access the encrypted part of the data. It was not a direct nuclear bomb threat, but a threat on a nuclear facility itself came as a very sensitive news. The second case of a direct announcement of hydrogen bomb-also debatable in whether they actually succeed-escalated tension between SK and NK. This is because nuclear threat. whether it be true, or whether it be seemingly insignificant, is a direct concern for South Korea for safety and welfare of it citizens. But there are signs that NK wants to keep a current practically amiable relationship with SK. In Kim Jung Un's New Year Speech this year, he said "In the future, too, we will make strenuous efforts to develop inter-Korean talks and improve bilateral relations."  Economic sanctions and international isolation may work as a practical concern for North Korea to be more cautious on managing diplomacy with SK.
© Hailey Kwon. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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