On 30 November 1934, he was appointed Apostolic Delegate to Turkey and Greece and titular archbishop of Mesembria, Bulgaria. Thus, he is known as "the Turcophile Pope," by the Turkish society which is predominantly Muslim. Roncalli took up this post in 1935 and used his office to help the Jewish underground in saving thousands of refugees in Europe, leading some to consider him to be a Righteous Gentile (see Pope John XXIII and Judaism). In October 1935, he led Bulgarian pilgrims to Rome and introduced them to Pope Pius XI on 14 October.

When was he appointed Apostolic Delegate to Turkey and Greece?