This Pakistani 'Ghazanavi' missile is capable of delivering a nuclear bomb. (Photo: ISPR/AFP/Getty Images)

Developing nuclear weapons requires specialized equipment, expertise and technology. Once fissile material is acquired, a state has to develop a weapon design or assembly system, usually either a gun-type or an implosion bomb. Implosion weapons are more difficult to build but are also more efficient, as they produce larger yields and require less nuclear material. They use either plutonium or uranium plus high explosives arranged to form an imploding shock wave. The simpler gun-type device, fashioned after the mechanism in the artillery gun, is only practical using highly enriched uranium. This device was used by the Americans in 1945 in the Japanese city of Hiroshima. Iraq attempted to design an implosion bomb that would use highly enriched uranium; while North Korea chose to use enriched plutonium in its model for a nuclear weapon. In addition to actual weapons, a state must also have missiles, rockets or another delivery mechanism in order to be a nuclear threat. close window