ONUC was established initially in July 1960 to ensure the withdrawal of Belgian forces, to assist the Government in maintaining law and order, and to provide technical assistance. The function of ONUC was subsequently modified to include maintaining the territorial integrity and the political independence of the Congo, preventing the occurrence of civil war, and securing the removal from the Congo of all foreign military, paramilitary and advisory personnel not under the United Nations Command, and all mercenaries. On completion of the mandate, the Mission was withdrawn in June 1964.
Originally, the medal awarded for service in the Congo was a UN blue and white ribbon with a bar indicating Congo service. In 1963 it was decided that a distinctive ribbon should be issued. The ribbon subsequently awarded carries a broad centre band of green, symbolic of hope which was thought to be appropriate for a young nation, and also to represent the Congo Basin. The centre band is flanked by two narrow white bands, representing the UN Mission and at either end are two bars of UN blue. To qualify for the medal three months of service in the Mission were required.
Countries providing troops to this Mission were: Argentina, Austria,Brazil, Canada, Congo, Denmark, Ecuador, Ethiopia, Ghana, Greece, Guinea, India, Indonesia, Iran, Ireland, Italy, Liberia, Malaysia, Mali, Morocco, the Kingdom of the Netherlands, Nigeria, Norway, Pakistan, the Philippines, Sierra Leone, Sri Lanka, the Sudan, Sweden, Tunisia, the United Arab Republic and Yugoslavia.