A convention of IHL could be seen as the fresco of a new room where many different people have to live together. Everyone proposes his idea of the best way to decorate the future room. The chosen characteristic of the fresco could reveal single past experiences and individual hopes for the future. However, in this new room, all group members have to live together, so the final fresco represents a compromise between the exigences and the concept of beauty for everyone. With the end of the IIWW, the international community tried to paint this fresco to find shared or shareable juridical instruments so that what happened during the last war would not recur. The expression of such a purpose could be read in the preamble of the San Francisco Chart. But this is not the only. Another example could be the elaboration of the conventions of Geneva of 1949, and the iter followed to arrive at signing it in 1949. The text of 1949 is the product of more than ten years of meetings and projects that are not only interesting from a juridical point of view but also provide a unique perspective on the history of international relations from the Thirties to the beginning of the Fifthy. According to the documentation about Pius XII's pontificate, which scholars will have access to in 2020, this paper presents the Vatican Secretary's perspective on negotiating the Geneva Convention of 1949. The archival documentation shows an image of the Vatican Secretary who tries to find his position between the states in a new international order, characterized by the aftermath of World War II and the beginning of the Cold War. At the same time, through such input from outside, he reflects on his juridical and political character after the Lateran Treaty and the beginning of the Cold War. Besides that, this negotiation obliged the Holy See to consider, on the one hand, his past and future activities in the humanitarian relief field and, on the other, to measure itself with different actors.