President Obama’s historic visit to Hiroshima this week offers an opportunity to take a clear-eyed look back to the first and only time nuclear weapons have been used in war. Germany had surrendered on May 8, 1945. Japan refused to surrender and continued to wage the Pacific War. President Harry S. Truman faced a decision on whether or not to drop the world’s first atomic bomb in Japan.

“3: President Truman formed a committee of men to tell him if this bomb would work, and if so, what he should do with it. Some members of this committee felt that the bomb would jeopardize the future of civilization. They were against its use. Others wanted it to be used in demonstration on a forest of cryptomeria trees, but not against a civil or military target. Many atomic scientists warned that the use of atomic power in war would be difficult and even impossible to control. The danger would be very great. Finally, there were others who believed that if the bomb were used just once or twice, on one or two Japanese cities, there would be no more war. They believed the new bomb would produce eternal peace.”

This fragment is from Trappist monk and social justice and peace activist Thomas Merton’s 1962 prose poem “Original Child Bomb.” Its title is a rough translation of the root characters in the Japanese term for the atom. Merton subtitled his “anti-poem” “Points for meditation to be scratched in the walls of a cave,” and it includes a numbered list of 41 points about the atomic bomb’s creation, the decision to drop the first one on Hiroshima, and its aftermath:

“32: The bomb exploded within 100 feet of the aiming point. The fireball was 18,000 feet across. The temperature at the center of the fireball was 100,000,000 degrees. The people who were near the center became nothing. The whole city was blown to bits and the ruins all caught fire instantly everywhere, burning briskly. 70,000 people were killed right away or died within a few hours. Those who did not die at once suffered great pain. Few of them were soldiers.

33: The men in the plane perceived that the raid had been successful, but they thought of the people in the city and they were not perfectly happy. Some felt they had done wrong. But in any case they had obeyed orders. ‘It was war.’”

It was war, and despite the initial reaction by co-pilot Captain Robert Lewis as he witnessed the devastation — “My God, what have we done?” — pilots and crew members stressed over and over again that they believed they did what they had to do. But the bombs dropped on Hiroshima and Nagasaki have not produced eternal peace. Instead they opened a Pandora’s box that can never be fully locked back up.

I have visited Hiroshima twice — once with my husband and once with him and our three sons. The Hiroshima Peace Memorial (Genbaku Dome), created from the ruins of the only structure left standing near the bomb’s hypocenter, is a reminder of how far we still have to go to make this a world worthy of and safe for all our children.

The Bulletin of the Atomic Scientists’ “Doomsday Clock” has this ominous message today: it is still three minutes to midnight. Beginning in 1947 the clock’s hands have moved based on the scientists’ evaluation of whether events are pushing humanity closer to or further from nuclear apocalypse; since 2007 they have also considered climate change and other threats that might lead to global catastrophe. In 2015 the clock was moved closer to midnight because of grave concerns about unchecked climate change, global nuclear weapons modernizations, and outsized nuclear weapons arsenals. In January 2016 they announced it has not changed: “Last year, the Science and Security Board moved the Doomsday Clock forward to three minutes to midnight, noting: ‘The probability of global catastrophe is very high, and the actions needed to reduce the risks of disaster must be taken very soon.’ That probability has not been reduced. The Clock ticks. Global danger looms. Wise leaders should act—immediately.” Will we hear and heed?

President Obama’s visit should prompt us all to realize that if we do not want the horrors of Hiroshima and Nagasaki to be repeated ever again we cannot be complacent. While we can celebrate all steps that have been taken to control access to more weapons in our nuclear saturated world we must do even more to protect our children’s and grandchildren’s futures in a world rife with war and religious, racial, gender, sectarian, and political strife. When anyone argues that the world might be safer if more countries had nuclear weapons it is yet another reminder that history can and may repeat itself on our watch if we are not vigilant. The clock is still ticking.

The same year that “Original Child Bomb” was published, Thomas Merton also wrote this in the essay “Nuclear War and Christian Responsibility”: “. . . there can be no doubt that Hiroshima and Nagasaki were, though not fully deliberate crimes, nevertheless crimes. And who was responsible? No one. Or ‘history.’ We cannot go on playing with nuclear fire and shrugging off the results as ‘history.’ We are the ones concerned. We are the ones responsible. History does not make us, we make it—or end it.”

What we have wrought by trying to play God is still our responsibility. How will we write the next chapter?