Before April 19, 2005, Cardinal Josef Ratzinger talked warmly of retiring. He was looking forward to a leisurely life, with his books, his brother and his beloved gray cat back in ancient Regensburg, Germany, where he owned a house.

But his plans changed when he was elected to head the Roman Catholic Church, becoming Pope Benedict XVI. Retirement was forgotten; the expectation was that Ratzinger, now Benedict, would die occupying “the chair of Peter,” as the pope’s throne is known.

Monday, Benedict shocked the world by announcing he would step down at the end of February, the first pope to do that in nearly 600 years. That the decision was so startling speaks more about the history of the church he led than his longevity, which was never expected to match the eight years he served. Benedict XVI became pope two days after his 78th birthday, having already survived a stroke. He admitted then that his reign might be short. Most popes die in their 70s.

When Benedict steps down at 8 p.m. Feb. 28 in Rome, age 85 years, 318 days, he will have lived longer than all but three of his 264 predecessors. Pope John Paul II was a full year younger when he died in 2005.

“After having repeatedly examined my conscience before God, I have come to the certainty that my strengths, due to an advanced age, are no longer suited to an adequate exercise of the Petrine ministry,” Benedict said Monday.

He went on to note: “In today’s world, subject to so many rapid changes and shaken by questions of deep relevance for the life of faith, in order to govern the bark of Saint Peter and proclaim the Gospel, both strength of mind and body are necessary, strength which in the last few months, has deteriorated in me to the extent that I have had to recognize my incapacity to adequately fulfill the ministry entrusted to me. For this reason, and well aware of the seriousness of this act, with full freedom I declare that I renounce the ministry of Bishop of Rome, Successor of Saint Peter, entrusted to me by the Cardinals on 19 April 2005.”

Global reaction was immediate and respectful. President Barack Obama thanked him on behalf of all Americans and said, “I have appreciated our work together over these last four years.”

German Chancellor Angela Merkel said: “If the pope himself has now, after thorough consideration, come to the conclusion that he no longer has sufficient strength to exercise his office, that earns my very highest respect. In our time of ever-lengthening life, many people will be able to understand how the pope as well has to deal with the burdens of aging.”

French President Francois Hollande called it “a humane decision and one tied to a desire that must be respected.” A spokesman for Israel’s Chief Rabbi Yona Metzger told the Agence France-Presse news service that under Pope Benedict XVI, Judaism and Catholicism “became much closer . . . leading to a decrease in anti-Semitism around the world.”

The move makes him the first pope since Gregory XII in 1415 to retire. As that retirement came during a power struggle between Rome and France, when there were actually two and, for a short while, three popes, some church officials argue that the last pope to retire was Celestine V in 1294.

In fact, that it is possible for a pope to retire is thanks to Celestine V, a former hermit who served only five months and was imprisoned (and, legend has it, murdered) not long after leaving the office on orders of his successor. One of a handful of accomplishments by Celestine V was to write the canon that allows retirement, which noted ill health as a possible reason.