A look back at Pope Benedict XVI

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  A photo taken in 1943 during World War II shows Joseph Ratzinger as a German Air Force assistant. Pope Benedict XVI announced on February 11, 2013 he will resign as leader of the world's 1.1 billion Catholics on February 28 because his age prevented him from carrying out his duties -- an unprecedented move in the modern history of the Catholic Church. STR / AFP/Getty Images

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  This handout picture released by the Vatican Press Office on February 11, 2013 shows Pope Benedict XVI addressing an ordinary consistory at the Vatican the same day. Pope Benedict XVI announced he will resign on February 28, a Vatican spokesman told AFP, which will make him the first pope to do so in centuries. - / AFP/Getty Images

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  A file picture taken on April 6, 2006 shows Pope Benedict XVI saluting the believers during a meeting with young Catholics in St Peter's Square at the Vatican in preparation of the XXI World Youth Day. ALBERTO PIZZOLI / AFP/Getty Images

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  A file handout photo taken on March 28, 2012 and released by the Osservatore Romano shows Pope Benedict XVI arriving for the holy mass at Revolution Square in Havana. OSSERVATORE ROMANO / AFP/Getty Images

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  A file picture taken on May 12, 2009 shows Pope Benedict XVI praying at the Western Wall in Jerusalem's Old City. RONEN ZVULUN / AFP/Getty Images

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  In this photo provided by the Vatican newspaper L'Osservatore Romano, Pope Benedict XVI delivers his message at the end of a meeting of Vatican cardinals, at the Vatican, Monday, Feb. 11, 2013. AP

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  A group of faithful of the Youth Group of San Lorenzo carry a wooden cross in St Peter's Square to recite their daily rosary, at the Vatican, Monday, Feb. 11, 2013. Alessandra Tarantino / AP