After the Great War of 1914 – 1918 many YCS-movements were founded in several European countries. All this happened within the framework of the “Catholic Action”, the answer of the Church to the growing secularisation of the society. To give lay people the possibility to participate at the Church, people could be saved from the godless socialism and communism. So the Catholic Church could hold its grip at the faithful people and aimed a renewal of the spiritual life, a re-Christianisation of the society.
An important role was played by Jozef Cardijn, the chaplain of the YCW, who was in favour of the specialised Catholic Action. He promoted separated youth organisations according to the(ir) professions (of their parents) : JOC / YCW (workers), JAC / MIJARC (farmers), JIC (independent), JUC (students) and JEC / YCS (secondary students).
Wars are many times caused by a narrow nationalism, prejudices, ignorance, … After the Second World War, young people saw in international exchanges a possibility to avoid more wars. By meeting each other in a friendly way, by exchanging experiences and opinions, you learn to know each other better and you can take away the basis of conflicts.
Inspired by the example of the YCW, also YCS-groups wanted to make contact with each other. The first steps were taken by the Canadian YCS that hold out its hand to the French YCS just after WW II. During mutual visits they noticed their similarities although they lived in two different realities.
In 1946 René Remond of the JEC France and Gérard Pelletier of the JEC Quebec decided to bring together several national YCS-movements on the occasion of the 25th anniversary of Pax Romana in Fribourg.
From the 1st till 8th September 1946, 30 responsibles and chaplains from YCS-movements from France, Canada, the USA, Flanders and Wallonia gathered to take the first steps for further collaboration. Other sources mention also the participation of representatives of Luxembourg, Italy, Switzerland and Czechoslovakia.
Unanimously they expressed the wish to start a common work and they decided to establish the “International Commission of YCS”, composed by presidents and chaplains of the national member movements. As secretariat and executive body they created the “CIDI”, the International Documentation and Information Centre in Paris. Here they collected all kinds of information about Catholic Action, working methods, … that could be consulted by YCS-movements. They were also responsible for helping countries were there was no Catholic Action for students and for organising international meetings.
The years after, the optimism was tempered by the Cold War. The movements were personally hit by the disappearance of the Czech YCS after the putsch in Prague in 1948. Another evolution in that period was the growing awareness of the colonies, the desire for independence. Also within the CIDI there were similar developments. Not only in Europe and North-America the YCS was growing, but also in the Third World young people showed interest in the YCS, like in Brazil, Cuba, Peru, Chile, Lebanon, … . The formula of the CIDI was too limited for such an expansion and did not allow to be an organisation to represent the catholic students to the outside world.