Wikipedia dit que cette prière date de 1912; publiée en France
en Dec 1912 dans la revue La Clochette.
La prière fut transmise au Pape Benoit XV.
La traduction en Italien est publiée en Jan 1916 en première page de
Osservatore Romano.

Summarising the Christian Renoux' book on the prayer, an article by Egidio Picucci on the 19-20 January 2009 issue of L'Osservatore Romano says that the earliest record of the prayer is its appearance, as "a beautiful prayer to say during Mass" in the December 1912 number of the small devotional French publication La Clochette, "the bulletin of the League of the Holy Mass". In 1915, Marquis Stanislas de La Rochethulon, president of the Anglo-French association Souvenir Normand, which called itself "a work of peace and justice inspired by the testament of William the Conqueror, who is considered to be the ancestor of all the royal families of Europe", sent this prayer to Pope Benedict XV. The Pope had an Italian translation published on the front page of L'Osservatore Romano of 20 January 1916. It appeared under the heading, "The prayer of Souvenir Normand for peace", and with the explanation: "Souvenir Normand has sent the Holy Father the text of some prayers for peace. We have pleasure in presenting in particular the prayer addressed to the Sacred Heart, inspired by the testament of William the Conqueror". On 28 January 1916, the French newspaper La Croix reprinted, in French, the Osservatore Romano article, with exactly the same heading and explanation. La Rochethulon wrote to the newspaper to clarify that it was not a prayer of Souvenir Normand, but he chose not to mention La Clochette, the first publication in which it had appeared. Because of its appearance on L'Osservatore Romano and La Croix as a prayer for peace during the First World War, this prayer then became widely known.

Wikipedia: search/ Prayer of St Francis