Pope Francis in April 2015, at a special mass in St. Peter's Basilica marking the centenary of the events, described atrocities against Armenian civilians in 1915–1922 as "the first genocide of the 20th century". In protest, Erdoğan recalled the Turkish ambassador from the Vatican, and summoned the Vatican's ambassador, to express "disappointment" at what he called a discriminatory message. He later stated "we don’t carry a stain or a shadow like genocide". US President Barack Obama called for a "full, frank and just acknowledgement of the facts", but again stopped short of labelling it "genocide", despite his campaign promise to do so.