The United Nations Operation in the Congo (ONUC) was a United Nations peacekeeping force in the Democratic Republic of the Congo that was established on 14 July 1960 and was withdrawn in 1964. The peacekeeping mission began in response to the Congo Crisis, during which the central government of Congo-Leopoldville faced rebellion from the secessionist states of Katanga and South Kasai. The United Nations sent several peacekeeping soldiers to enforce the peace in the region; by 31 July 1960, there were 11,000 UN troops in the Congo. The ONUC peacekeeping mission was the first significant UN military mission, and it took part in Operation Morthor (which resulted in the massacre of 30 innocent people at Radio Katanga) and the Siege of Jadotville (which resulted in the surrender of the 158-strong Irish garrison). However, Operation Grandslam put an end to Moise Tshombe's Katangese uprising, and ONUC withdrew from the Congo in June 1964 after the defeat of Katanga had been completed in 1963.