Although the one-party regime in North Korea has maintained its hold on the country, North Korea has experienced changes in leadership. We can assume that such changes of supreme leaders also make possible a change in policies toward the US and nuclear issues. Kim Il-Sung, the first supreme leader, looked for dialogue with the U.S. and denuclearization of the Korea peninsula. However, Kim Jong-Il, Kim Il-Sung’s successor, had an adversarial attitude towards the U.S. during the first nuclear crisis in 1993. Kim Jong-Il declared that he would develop nuclear weapons during the second nuclear crisis in 2003 after Kim Il-Sung’s death. We can see that Kim Jong-Il has made policies toward the US more hardline than those of Kim Il-Sung. We can say that that is why Kim Jong-Il personally had an adversarial attitude towards the U.S. from the first crisis onward.