Speaking to the faithful gathered in St. Peter’s Square, Francis recalled the “horror and repulsion” aroused by the twin bombings of Nagasaki on Aug. 9 1945, and Hiroshima, three days earlier.

“This (event) has become the symbol of mankind’s enormous destructive power when it makes a distorted use of scientific and technical progress,” he said.

More than 70,000 people were killed when U.S. forces dropped an atomic bomb on Nagasaki. The bomb that hit Hiroshima left an estimated 140,000 people dead.

The attacks marked a turning point in the Second World War, prompting Japan to surrender to the Allies, although Japanese civilians continued to suffer from disease and disability long after the bombings.

Reflecting on the legacy of the series of events, the Pope said: “(It) serves as a lasting warning to humanity so that it forever rejects war and bans nuclear weapons and all arms of mass destruction.”

Francis marked the anniversary by renewing calls for global peace, appealing for dialogue in the place of violence.

“With war one always loses,” he said. “The only way to win a war is never to wage it.”

Diplomatic relations were formed between Japan and the Vatican in 1942, during the height of the Second World War. Nearly 40 years later, Pope John Paul II visited Hiroshima, where he read a peace message in Japanese and other languages.