His apparent weight loss had also been a subject of many guesses. Some South Korean reports cited pancreatic cancer, while others inferred that he was going through a rigorous diet program to prevent another stroke.
Much like his heir apparent son, Kim held several high posts in the government before formally leading the communist nation. After the death of his father, Kim became chairman of the North Korea's National Defense Commission, which was considered the highest declared position within the government.
Kim soon led the Communist Worker's Party, which sealed his position as leader of the country.
Kim's nuclear weapons stronghold and his strategic partnerships within the region were viewed as a threat by many democratic governments. Kim cited national security reasons for his nuclear weapons production program. In 2006, his regime successfully executed its first underground nuclear test.
Conflicts between North and South Korea continued throughout Kim's rule. Tensions seemed to have cooled in recent years as South Korea sent humanitarian aid through U.N. agencies to help alleviate the famine in North Korea. Talks between the two nations' leaders seemed to have added to the illusion.
Still, Kim moved forward with his nuclear weapons program. In 2002, President George W. Bush said in his State of the Union address that North Korea was part of the "axis of evil," along with Iraq and Iran.
Hopes for reconciliation between the two nations diminished when North Korea attacked the South Korean island of Yeonpyeong, killing two South Korean marines and two civilians.
South Korea's military has been put on alert following the death announcement.
The White House said in a short public statement that it is in close contact with South Korea, and it is "closely monitoring" reports of the death. There are currently about 29,000 U.S. troops stationed in South Korea.