This book delves into the history of how the Catholic Church’s leadership, both in the Vatican and in the Latin Patriarchate of Jerusalem, responded to the emerging conflict between Zionism and Palestinian nationalism for the future of the Holy Land. Beginning with the Balfour Declaration of 1917 and the conquest of Jerusalem by the Allied forces, it traces how the popes, Benedict XV (1914-1922) as well as Pius XI (1922-1939), anxiously and skeptically regarded British designs for what would become Mandatory Palestine. Through the economic crisis of the late 1920s, the violent clashes of the Arab Revolt, and ending with the outbreak of the Second World War, it examines how the relationship between the local Catholic community and British government officials developed, from evictions and expropriations following wartime upheavals to a careful co-operation filled with mistrust and tensions. Likewise, it investigates how the escalating hostility and violence between the Jewish and Muslim sections of the population influenced the interreligious relations between them and Catholics. Based on research in the Vatican Archives, it offers novel perspectives on the shifting policies of the Vatican, the maneuvrings of European governments and the schemes of the Latin Patriarch of Jerusalem, Luigi Barlassina, to further their interests in the struggle for the future of the Holy Land.