In September United Nations troops launched Operation Morthor, bringing them into conflict with Katangese forces. Though Welensky had abided by previous instructions from Macmillan to refrain from troop deployments, the British High Commissioner gave him permission this time, and Welensky moved ground troops and most of the RRAF to the frontier. United Nations Secretary General Dag Hammarskjöld, hoping to negotiate a solution to Katanga's secession, agreed to meet Tshombe at Ndola. However, Hammarskjöld's plane was shot down from Rhodesian territory close to Ndola in November 1961, and he was killed. Welensky was subsequently blamed for the accident throughout the communist and Afro-Asian world, becoming a hated figure and a lingering symbol of colonialism. Other UN officials reached a ceasefire agreement with Tshombe in Ndola, and Macmillan thanked Welensky for facilitating the meeting.