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.

Johan Willem Beyen, Minister for Foreign Affairs of the Netherlands from 1952 to 1956.

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 1 June 1955, the first day of the Messina Conference, the representatives of the six Member States of the European Coal and Steel Community (ECSC) analyse the joint memorandum, officially forwarded to them on 20 May 1955 by the Belgian, Luxembourg and Netherlands Governments, in which the three Benelux countries call for greater economic integration in Europe, particularly in the areas of transport, energy and the peaceful use of nuclear power.

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).