On 5 May 1953, Johan Willem Beyen, Netherlands Foreign Minister, sends a letter to his counterparts in the Member States of the European Coal and Steel Community (ECSC) in which he outlines the means for establishing general, rather than sectoral, economic integration in order to establish progressively a genuine common market in Europe.

In May 1953, young members of the Belgian Branch of the European Movement demonstrate on the streets of Liège in favour of the abolition of frontiers and customs controls in Europe.

On 20 May 1955, the Belgian daily newspaper Le Soir outlines the main proposals for a revival of European integration set out in the joint memorandum from the three Benelux countries to the six Member States of the European Coal and Steel Community (ECSC).