6 August 1960
On 6 August 1960, the United Nations (UN) Secretary General, Mr. Dag Hammarskjöld, asked the UN Security Council to lay down rules which would allow UN forces to enter Katanga without interfering with Congo’s internal affairs. The move by Hammarskjöld followed the adoption of Resolution 143 by the UN Security Council, which demanded the withdrawal of Belgian troops and calling for UN military support for the Congolese Army. Ireland and Ghana were among the countries who pledged to provide support. The Congolese President, Patrice Lumumba demanded the immediate removal of Belgian forces in his country. He threatened to ask the Soviet Union for help should the Belgian troops refuse to obey the resolution. A day after the resolution was made, UN troops arrived in Congo. Initially there were 1200 soldiers from 24 countries.  
References

The Star, (6 August 1960), Dag wants troops in Katanga “without upsetting Congo” [Available at the National Library of South Africa, Cape Town Campus] pg1.