Long before he became Pope, Archbishop Angelo Roncalli knew the JOC from his time as Nuncio in France in the late 1940s and early 1950s, when he had regular meetings with Fr Georges Guérin and other YCW leaders.
As Pope, he accepted Cardijn's proposal to draft an encyclical to mark the 70th anniversary of Rerum Novarum, publishing Mater et Magistra in May 1961.
"I want the Y.C.W. more than Pius Xl, more than Pius XII It will save the working youth ".
- Pope John XXIII, 1962