the control of the Korean People's Army and the security forces by his loyal agent, Defence Minister Oh Jin-wu. Kim Jong-il explains in Socialism of Our Country is Socialism of Our Style as the Embodiment of the Juche Idea, a speech made to the central committee of the WPK on December 27, 1990, the divorce with Marxism–Leninism. "We could not literally accept the Marxist theory which had been advanced on the premises of the socio-historic conditions of the developed European capitalist countries, or the Leninist theory presented in the situation of Russia where capitalism was developed to the second grade. We had had to find a solution to every problem arising in the revolution ... from the standpoint of Juche". The practical effect of Juche was to seal the DPRK off from virtually all foreign trade, except to a limited extent with China and the Soviet Union. But, the economic reforms of Deng Xiaoping in China after 1978 meant that trade with the undeveloped centrally-planned economy of the DPRK held decreasing interest for China, while the fall of communism in the Soviet Union in 1991 completed the DPRK's isolation. This, added to the continuing high level of expenditure on armaments, led to a steadily mounting economic crisis from the 1980s onwards. The rise of Kim Jong-il Kim Jong-il had been groomed to become his father's successor for a long time. In 1964, he was appointed Central Committee member, then promoted to Politburo member and designated successor to Kim Il-sung in 1974 by a Central Committee plenum. After Kim Jong-il assumed the position of party secretary in charge of organization and propaganda in September 1973, his involvement in party affairs enhanced their organizational strength and discipline. With his elevated position in the party, Kim Jong-il rigidly implemented two policies: an enhancement of the role of full-time party cadres in local and administrative units and a strengthening of party-life criticism in every unit of the workplace as well as in the party. This establishment of a strong disciplinary tradition in the party contributed to the maintenance of social control. It has become an important foundation for the persistence of the existing authority structure centered on the father and the son. In 1980, the WPK Congress elevated Kim Jong-il to senior positions and publicized his status as heir apparent. Until then, it seemed likely that Kim's successor would be either Oh Jin-wu or