The Angelus is not identical to the "Noon Bell" ordered by Pope Calixtus III (1455–58) in 1456, who asked for a long midday bell-ringing and prayer for protection against the Turkish invasions of his time. In his 1956 Apostolic Letter "Dum Maerenti Animo" about the persecution of the Catholic church in Eastern Europe and China, Pope Pius XII recalls the 500th anniversary of the "Noon Bell", a prayer crusade ordered by his predecessors against what they considered to be dangers from the East. He again asks the faithful throughout the world, to pray for the persecuted Church in the East during the mid-day Angelus.