After days of clashes at roadblocks around Elisabethville, in which a Swedish peacekeeper was killed, UN forces went on the offensive on December 5, 1961, against the gendarmes and mercenaries of Moise Tshombe's secessionist State of Katanga. The fighting lasted until December 21, when Tshombe signed the Kitona Declaration accepting that Katanga was part of the Congo, a pledge he soon backed away from.
The Congo Crisis had already claimed the life of UN Secretary-General Dag Hammarskjöld, whose plane crashed under mysterious circumstances near Ndola just weeks earlier, on September 18, 1961, while he was en route to negotiate with Tshombe. Operation Unokat brought fierce urban combat to Elisabethville, where UN peacekeepers, deployed under a mandate to prevent civil war, found themselves conducting offensive operations against Katangese gendarmes and European mercenaries.
Katanga's secession bid was never simply a local affair. Belgian mining interests, particularly the powerful Union Minière du Haut-Katanga, had strong incentives to keep the province's mineral wealth out of the hands of the central government in Léopoldville, and mercenaries from Belgium, France, and Rhodesia fought alongside Tshombe's forces.
The Kitona Declaration that ended the fighting proved hollow. Fighting resumed in 1962, and Katanga's secession was only fully crushed in January 1963 when UN forces captured Kolwezi. The episode became a case study in how newly independent African nations were destabilized by the collision of Cold War politics and colonial-era economic interests.