Nuns pray as they wait for Pope Benedict XVI's last Angelus prayer, in St. Peter's Square, at the Vatican, Sunday, Feb. 24, 2013. Benedict XVI gave his pontificate's final Sunday blessing from his studio window to the cheers of tens of thousands of people packing St. Peter's Square, but sought to reassure the faithful that he wasn't abandoning the church by retiring to spend his final years in prayer. The 85-year-old Benedict is stepping down on Thursday evening, the first pope to do so in 600 years, after saying he no longer has the mental or physical strength to vigorously lead the world's 1.2 billion Catholics. (AP Photo/Domenico Stinellis)
World reacts to Pope's resignation
Pope Benedict left the Catholic world in shock after becoming the first pontiff since the Middle Ages to resign his office, saying that failing strength had left him unable to lead the church through a period of relentless change and turmoil.