Powers became evident as a result of the rigged 1947 Polish legislative election which constituted an open breach of the Yalta Agreement, followed by the announcement of the Truman Doctrine on 12 March 1947. On 4 March 1947 France and the United Kingdom signed the Treaty of Dunkirk for mutual assistance in the event of future military aggression in the aftermath of World War II against any of the pair. The rationale for the treaty was the threat of a potential future military attack, specifically a Soviet one in practice, though publicised under the disguise of a German one, according to the official statements. Immediately following the February 1948 coup d'état by the Communist Party of Czechoslovakia, the London Six-Power Conference was held, resulting in the Soviet boycott of the Allied Control Council and its incapacitation, an event marking the beginning of the Cold War. The remainder of the year 1948 marked the beginning of the institutionalised modern European integration. Initial years (1948–57) With the start of the Cold War, the Treaty of Brussels was signed in 1948 establishing the Western Union (WU) as the first organisation, followed by the International Authority for the Ruhr. In the same year, the Organization for European Economic Co-operation, the predecessor of the OECD, was also founded to manage the Marshall Plan; the Eastern Bloc responded with establishing the Comecon. A pivotal moment in European integration was the Hague Congress of May 1948, as it led to the creation of the European Movement International, the College of Europe and most importantly to the founding of the Council of Europe on the 5th of May 1949 (now known as Europe Day). The Council of Europe was the first institution to bring the sovereign nations of Western Europe together, raising great hopes and fevered debates in the following two years for further European integration. It has since been a broad forum to further cooperation and shared issues, achieving things like the 1950-signed European Convention on Human Rights. Essential for the actual birth of the institutions of the EU was the 9th of May 1950 Schuman Declaration (on the day after the fifth Victory Day, today's Europe day – of the EU). On the basis of that speech, France, Italy, the Benelux countries (Belgium, Netherlands and Luxembourg) together with West Germany signed the Treaty of Paris (1951) creating the European Coal and Steel Community the following year;