The United Nations Operation in the Congo (known by the French acronym ONUC: 'Operation des Nations Unies au Congo') was established on 14 July 1960 by Security Council Resolution 143 and dissolved 30 June 1964. The headquarters of the Operation were located in Leopoldville (now Kinshasa) in the Republic of Congo.
The initial mandate of ONUC was to ensure the withdrawal of Belgian forces from the Republic of the Congo, to assist the Government in maintaining law and order and to provide technical assistance. The function of ONUC was subsequently modified to include maintaining the territorial integrity and political independence of the Congo, preventing the occurrence of civil war and securing the removal from the Congo of all foreign military, paramilitary and advisory personnel not under the United Nations Command, and all mercenaries.
ONUC included, in addition to a peacekeeping force which comprised at its peak strength nearly 20,000 officers and men, an important Civilian Operations component. Originally mandated to provide the Congolese Government with the military and technical assistance it required following the collapse of many essential services and the military intervention by Belgian troops, ONUC became embroiled by the force of circumstances in a chaotic internal situation of extreme complexity and had to assume certain responsibilities which went beyond normal peacekeeping duties.
The instructions of the Security Council to this Force were strengthened early in 1961 after the assassination in Katanga province of former Prime Minster Patrice Lumumba. The Force was to protect the Congo from outside interference, particularly by evacuating foreign mercenaries and advisers from Katanga and preventing clashes and civil strife, by force if necessary as a last resort. Following the reconvening of Parliament in August 1961 under United Nations auspices, the main problem was the attempted secession, led and financed by foreign elements, of the province of Katanga. In September and December 1961, and again in December 1962, the secessionist gendarmes under the command of foreign mercenaries clashed with the United Nations Force. Secretary-General Dag Hammarskjold lost his life on 17 September 1961 in the crash of his airplane on the way to Ndola (in what is now Zambia) where talks were to be held for the cessation of hostilities. In February 1963, after Katanga had been reintegrated into the national territory of the Congo, a phasing out of the Force began.
The following individuals served as Special Representatives of the Secretary-General: Ralph J. Bunche (United States) July - August 1960; Andrew W. Cordier (United States) August - September 1960; Rajeshwar Dayal (India) September 1960 - May 1961; Mekki Abbas (Sudan) (Acting) March - May 1961. The officers in charge were: Sture Linner (Sweden) May 1961- January 1962; Robert K.A. Gardiner (Ghana) February 1962 - May 1963; Max H. Dorsinville (Haiti) May 1963 - April 1964; Bibiano F. Osorio-Tafall (Mexico) April - June 1964. The following individuals served as Force Commanders: Lieutenant-General Carl C. von Horn (Sweden) July - December 1960; Lieutenant-General Sean MacEoin (Ireland) January 1961 - March 1962; Lieutenant-General Kebbede Guebre (Ethiopia) April 1962 - July 1963; Major-General Christian Roy Kaldager (Norway) August - December 1963; Major-General Johnson Aguiyu Ironsi (Nigeria) January - June 1964.