The nuclear programme was personally directed during his lifetime by Kim Il Sung. Responsibility for its implementation was strictly controlled by the state and military apparatus, with no role for the rubber-stamp Supreme People's Assembly.
Research has been centred on Yongbyon, 60 miles north of the capital, Pyongyang. Western intelligence agencies believe North Korea already has enough plutonium for one or two crude nuclear bombs, and could produce much more if it reprocessed the 8,000 fuel rods it recently removed from the country's main reactor.
North Korea has always claimed that its construction of a small experimental reactor was part of a drive towards electricity generation, but informed observers say the five megawatt reactor built subsequently has never been connected to the national grid.