After the signing of the Atlantic Charter and the Declaration of the United Nations, the Conference of Allied Ministers of Education (CAME) began meetings in London which continued between 16 November 1942 to 5 December 1945. On 30 October 1943, the necessity for an international organization was expressed in the Moscow Declaration, agreed upon by China, the United Kingdom, the United States and the USSR. This was followed by the Dumbarton Oaks Conference proposals of 9 October 1944. Upon the proposal of CAME and in accordance with the recommendations of the United Nations Conference on International Organization (UNCIO), held in San Francisco in April–June 1945, a United Nations Conference for the establishment of an educational and cultural organization (ECO/CONF) was convened in London 1–16 November 1945 with 44 governments represented. A prominent[clarification needed] figure in the initiative for UNESCO was Rab Butler, the Minister of Education for the United Kingdom. At the ECO/CONF, the Constitution of UNESCO was introduced and signed by 37 countries, and a Preparatory Commission was established. The Preparatory Commission operated between 16 November 1945, and 4 November 1946—the date when UNESCO's Constitution came into force with the deposit of the twentieth ratification by a member state.