The European Union (the predecessor of the European Union) was formally established in 1967. In the 1970s, two things were more important:

1.*** homomorphic expansion; 1973, Britain, Ireland and Denmark joined the EC, and the number of EC members changed from six to nine, which was the first enlargement of the EC.

2. Copenhagen Report; With the smooth development of European economic integration, member countries began to seek political integration. 1973 13 In February, the G-9 Summit was held in Copenhagen, Denmark. The meeting published the European Identity Report, which put forward the famous slogan "Western European countries should speak with one voice". The Copenhagen Report is the first document that the European Community has adopted an independent position in international affairs, and this meeting has also become a milestone in the political integration of European countries.

I hope it helps you!