Pope Leo XIV returned to the balcony where he was presented to the world as the new leader of the Roman Catholic church just days ago, using his first Sunday address to the faithful to call for peace.

“Never again war,” he said to a roar from the tens of thousands who had gathered in St. Peter’s Square at noon. Leo’s appeal was addressed to the world’s most powerful leaders, and he noted that it had been almost 80 years to the day since the “immense tragedy” of World War II had ended. He quoted Pope Francis, his predecessor, who often referred to the current global wave of violence as “a third world war in pieces.”

Leo was elected pope on Thursday, becoming the first American pontiff on the second day of the conclave. Since then, he has had a busy calendar, with Vatican observers watching closely for clues on how he plans to lead.

On Friday, with the cardinals who had elected him the previous day, he celebrated his first Mass in the Sistine Chapel as pope. In his homily, he pledged to align himself with “ordinary people.”

The pope met with the cardinals again on Saturday, saying he would continue the work of Francis in steering the church toward greater collegiality and a focus on caring for marginalized people.

On Sunday, he continued to echo themes that Francis spoke about regularly in his Sunday addresses, including the wars in Ukraine and Gaza.