Pope Francis, left, is greeted by the head of Armenia's Orthodox Church Karekin II, during an Armenian-Rite Mass on the occasion of the commemoration of the 100th anniversary of the Armenian Genocide, in St. Peter's Basilica, at the Vatican, Sunday, April 12, 2015. Historians estimate that up to 1.5 million Armenians were killed by Ottoman Turks around the time of World War I, an event widely viewed by genocide scholars as the first genocide of the 20th century. Turkey however denies that the deaths constituted genocide, saying the toll has been inflated, and that those killed were victims of civil war and unrest. (AP Photo/Gregorio Borgia)