ONUC
Although a manifest pacifist and a devout Buddhist, Thant did not hesitate to use force when required. During the Congo Civil War in 1962, Katangan secessionists led by Moise Tshombe repeatedly attacked UN Operation in the Congo forces (ONUC). In December 1962, after ONUC suffered a sustained four-day attack in Katanga, Thant ordered the "Operation Grandslam" to gain "complete freedom of movement for ONUC all over Katanga." The operation proved to be decisive and ended the secessionist insurgency once and for all. By January 1963, the secessionist capital Elizabethville was under full UN control. In his speech at Columbia University Thant expressed expectation of completion of the United Nations Operation in the Congo in mid 1964.