European cooperation was not just in the field of economic affairs or customs; it also involved military aspects.
In Dunkirk, on 4 March 1947, France and the United Kingdom signed a mutual assistance pact. Set in the post-war climate, this friendship and cooperation treaty was openly targeted at vanquished Germany in order to forestall any new aggression on its part. The French Government sought to guard against what it still considered a potential threat from across the Rhine.
However, in the following months, tension continued to rise between the Western and Soviet blocs. In October, the recently-created Cominform took a fiercely critical stance towards the aid provided by the Marshall Plan, unveiled by the United States in June 1947, for the rebuilding of Europe. Cominform officials condemned what they regarded as the subservience of Europe to America, and both the USSR and its satellite countries refused help from the Marshall Plan. The Western European countries, wanting above all to stop communist expansion, sought to convince Washington that it should grant temporary financial and material aid to the Western democracies that had been seriously weakened by five years of war.
On 22 January 1948, Ernest Bevin, British Foreign Secretary, delivered a speech to the House of Commons in which he condemned the Soviet threat and asserted his determination to further the United Kingdom’s cooperation with France and the Benelux countries through a Western Union that would expand the Dunkirk Treaty. A few days later, the Prague coup of 25 February 1948, when the communists forcibly seized power in Czechoslovakia, only heightened international tension and the dangers arising from the Cold War.
The United States quickly made known its preference for a regional pact which would exceed mere military matters. Talks were immediately begun during which the British Government unveiled to France and the Benelux countries a plan for a mutual defence alliance in the event of external aggression.
On 17 March 1948, the five countries signed the Brussels Treaty establishing Western Union, designed to guard against any armed aggression in Europe (i.e. not including the overseas territories), no longer just from Germany, against any of its members.
At the same time, Denmark, Norway and Sweden discussed the idea of military cooperation within a Scandinavian defence union. Inspired by Finland’s experience, but remaining divided about their neutral status, these countries wanted to protect themselves against any possible Soviet pressure and considered calling on the United States to provide them with the armaments required to deter any attack. But the regional plan failed once and for all in 1949 when the Americans announced their unequivocal refusal to arm a neutral alliance.
The Brussels Treaty, scheduled to remain in force for 50 years, provides for the organisation of cooperation amongst the five signatories in the military, economic, social and cultural spheres. A united Military High Command of Western Union, a kind of joint HQ, was created. However, the Brussels Treaty was soon left devoid of its newly-expanded authority when a succession of treaties was signed which established the Organisation for European Economic Cooperation (April 1948), the North Atlantic Treaty Organisation (April 1949), the Council of Europe (May 1949) and the European Coal and Steel Community (April 1951). However, although the Brussels Treaty failed to create a customs union, it did partially meet the concerns of the Americans, who considered that it reinforced the position and willingness of the five member countries, all keen to receive economic and military aid from the United States.