Kim conducted a pursuit of nuclear weapons technology

The existence of North Korea's nukes continued to be a global concern. It was widely believed that the Kim dictatorship was using it as a negotiating point to obtain financial assistance and to prevent the development of tensions with South Korea, which were already present. The nation revealed that such a weapon has undergone an underground test in October 2006. After several years of talks being put on hold, a new agreement was reached in 2007. However, it was unclear how to verify North Korea's compliance with the agreement. When Lee Myung-bak was elected president of South Korea in December 2007, inter-Korean ties began to deteriorate once more as a result of Lee's tougher stance toward his North Korean counterpart.

North Korea continued sporadic weapons tests during the following few years, including a second underground nuclear test in May 2009. Several times, most notably in 2010, when the South Korean destroyer Cheonan was sunk close to the maritime boundary in March and two South Korean marines were killed during a military skirmish on Yeongpyeong Island in the same region in November.