 On 14 July 1960 , in response to requests by Prime Minister Lumumba , the UN Security Council adopted United Nations Security Council Resolution 143 . This called upon Belgium to remove its troops and for the UN to provide ' military assistance ' to the Congolese forces to allow them ' to meet fully their tasks ' . Lumumba demanded that Belgium remove its troops immediately , threatening to seek help from the Soviet Union if they did not leave within two days . The UN reacted quickly and established the United Nations Operation in the Congo ( ONUC ) . The first UN troops arrived the next day but there was instant disagreement between Lumumba and the UN over the new force 's mandate . Because the Congolese army had been in disarray since the mutiny , Lumumba wanted to use the UN troops to subdue Katanga by force . Referring to the resolution , Lumumba wrote to UN Secretary General Dag Hammarskjöld , ' From these texts it is clear that , contrary to your personal interpretation , the UN force may be used to subdue the rebel government of Katanga . ' Secretary General Hammarskjöld refused . To Hammarskjöld , the secession of Katanga was an internal Congolese matter and the UN was forbidden to intervene by Article 2 of the United Nations Charter . Disagreements over what the UN force could and could not do continued throughout its deployment . 
