The spiritual leader of 1.2 billion Roman Catholics, Pope Benedict XVI, surprised the world Monday by saying he will resign at the end of the month “because of advanced age.”

It’s the first time a pope has stepped down in nearly 600 years.

“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,” said Benedict, 85, according to the Vatican.

The news startled the Catholic world and led to frenzied speculation about who would replace him, including a debate about the merits of naming a pontiff from the developing world, where the church continues to grow, versus one from Europe, where it has deep historical roots.

But that decision will not be made by Benedict, who will leave his post at 8 p.m. on February 28, said the Rev. Federico Lombardi, a Vatican spokesman.

“Before Easter, we will have the new pope,” he said.

While Benedict won’t be directly involved in his successor’s selection, his influence will undoubtedly be felt. He appointed 67 of the 117 cardinals that — as of Monday — are set to make the decision.