NAGASAKI, Japan (Reuters) - Pope Francis on Sunday called for the abolition of nuclear weapons during a visit to Japan’s western cities of Nagasaki and Hiroshima, the only two cities in the world subjected to atomic bombing during World War Two.

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Francis, the first pope to visit Nagasaki in 38 years and only the second in history, told a gathering in a park at the blast site that nuclear weapons are indefensible.

The city “makes us deeply aware of the pain and horror that we humans are capable of inflicting upon one another,” he added.

Here are facts about the bombings of August 1945. Japan surrendered on August 15, less than a week after the Nagasaki bombing, putting an end to the war.

Among the potential targets had been Japan’s ancient capital of Kyoto, but then Secretary of War Henry Stimson, who had known and loved the key cultural center, persuaded President Harry Truman against bombing it.

HIROSHIMA

Hiroshima was the headquarters of some military units and a major supply base. War planners calculated that the surrounding mountains would concentrate the force of the bomb and enhance its destructiveness.

At 8:15 a.m. on August 6, 1945, an American B-29 Superfortress bomber named “Enola Gay” - for the pilot’s mother - dropped a 10,000-pound (4,536-kg) uranium-235 bomb on Hiroshima, instantly killing about 78,000 people. By year-end, about 140,000 were dead, from an estimated population of 350,000.

The bomb, nicknamed “Little Boy”, exploded about 600 meters (1,969 ft) above the center of the city, unleashing a surge of heat reaching 4,000 degrees C (7,200 F) across a radius of about 4.5 km (2.8 miles).

In 2016, Barack Obama, the first incumbent U.S. president to visit Hiroshima, gave a speech emphasizing nuclear disarmament and met bombing survivors, embracing one elderly man, who wept.

NAGASAKI

Three days after the Hiroshima event, at 11:02 a.m. on August 9, the United States dropped a 10,000-pound (4,536-kg) plutonium-239 bomb, nicknamed “Fat Man”, on the major industrial and port city of Nagasaki, whose hilly geography concentrated the blast.

It exploded about 500 meters (1,640 ft) above the ground, instantly killing about 27,000 of an estimated population of 200,000. By year-end the number of deaths from acute radiation exposure reached 73,884.

TOTAL KILLED

By Aug. 2019, Japan had recognized the total of deaths from radiation illness and injuries in Hiroshima as 319,186 and in Nagasaki as 182,601. New names are added on the bombing anniversaries each year.