Any hopes that Kim, being a younger man, would be more reform-minded were quickly dashed. If anything, he tried to turn back the clock on his father's halting latter-day efforts toward liberalization. Some North Koreans even whispered that Kim had had his father killed to stop the reforms.
An even more reclusive figure than his father, Kim refused to give interviews, appeared infrequently in public and ventured outside North Korea only a few times in his life. He kept abreast of world events through the Internet (banned for ordinary citizens) with the aid of interpreters since the only foreign language he spoke was the Russian of his childhood.
In his last years, Kim did make some attempts to end his country's isolation and poverty. In 2000, he held a landmark summit in Pyongyang with then-South Korean President Kim Dae-jung, but he reneged on a promise to reciprocate with a visit to Seoul. That same year, U.S. Secretary of State Madeleine Albright became the highest-level American official to visit Pyongyang since the end of the Korean War in 1953.
Albright later wrote that she found Kim to be an "intelligent man who knew what he wanted. He was isolated, not uninformed. Despite his country's wretched condition, he didn't seem a desperate or even a worried man. He seemed confident."
The rapprochement between Washington and Pyongyang faltered when Bush took office and condemned North Korea as part of an "axis of evil" along with Iran and Iraq.
Nevertheless, the Bush administration in October 2008 removed the country from a blacklist of "terror-sponsoring" nations in return for an agreement allowing limited inspections of nuclear sites there.
Kim's personal life was marked by disappointment. He lived for many years with a divorced actress, Song Hye Rim, the mother of his oldest son, Jong Nam, but they reportedly did not marry because Kim feared his father's disapproval. Song suffered from psychological problems and died in exile in Moscow.
Kim was reportedly devastated when Ko Yong Hi, the mother of his two younger sons, died of breast cancer in 2004. He also has a daughter with a woman who was his official wife but with whom he is believed never to have lived.
Details of Kim's personal life are sketchy. He rarely appeared in public with family members, but accounts from high-ranking defectors portrayed him as a doting father and partner who showered his loved ones with attention and kindness as though to compensate for his own father's distance.
"He is really a sensitive and arty type who ended up by birth floating through this world that is pure evil," said Michael Breen, author of "Kim Jong Il: North Korea's Dear Leader," one of the few English-language biographies of Kim.
PHOTOS: Kim Jong Il | 1942-2011
FULL COVERAGE: Kim Jong Il | 1942-2011