Career
He was ordained in 1906 and appointed Abbot of Montevergine, Italy in 1918. He served an Apostolic Visitor to Croatia during World War Two, in which capacity he worked on behalf of the Holy See for the protection of Croatian Jews. Marcone served as Nuncio in all but name.
He reported to Rome on the deteriorating conditions for Croatian Jews, made representations on behalf of the Jews to Croatian officials, and transported Jewish children to safety in neutral Turkey.
When deportation of Croatian Jews began, Stepinac and Marcone protested to Andrija Artuković. In his study of rescuers of Jews during the Holocaust, Martin Gilbert wrote, "In the Croatian capital of Zagreb, as a result of intervention by on behalf of Jewish partners in mixed marriages, a thousand Croat Jews survived the war.