More than seven decades after the United States waged nuclear war on civilians, the mushroom clouds of Hiroshima and Nagasaki haunt us still.

When President Barack Obama makes his trip to the Hiroshima Peace Memorial Park this Friday after a G-7 Summit, he must overrule his timorous advisers and issue an official presidential apology to the sons and daughters of Nippon.

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President Harry Truman’s atomic incineration of thousands of innocent men, women and children in Hiroshima and Nagasaki in August 1945 was a monstrous crime against humanity.

The Aug. 6 explosion in Hiroshima created a heat flash reaching several million degrees centigrade, vaporizing every shred of human flesh on anyone within half a mile of the blast’s center. Some 80,000 to 140,000 people died instantly. Another 100,000 were seriously injured.

In a radio broadcast hours later, Truman issued a chilling threat: “We are now prepared to obliterate more rapidly and completely every productive enterprise the Japanese have standing above ground in any city. We should destroy their docks, their factories and their communications. Let there be no doubt.”

On Aug. 9, a second atomic bomb hit Nagasaki. “Fat Man” detonated over the largest Roman Catholic church in East Asia, St. Mary’s Cathedral. It slaughtered an immediate 40,000 in the area. The final death toll was 50,000 to 70,000.

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The just war theory’s concept of ius in bello — or justice in war — maintains that when nations wage war on noncombatants, employ disproportionate or unreasonable force, or violate norms of civilized conduct, they commit acts indistinguishable from murder. Some historians believe that the Hiroshima and Nagasaki bombardments constitute state-sponsored terrorism — specifically because civilians were deliberately targeted and could not be considered collateral damage.

Fleet Adm. William D. Leahy, chairman of the Joint Chiefs of Staff during World War II, said, “It is my opinion that the use of this barbarous weapon at Hiroshima and Nagasaki was of no material assistance in our war against Japan. The Japanese were almost defeated and ready to surrender.”

Dwight D. Eisenhower strenuously urged Truman to “avoid shocking world opinion” by using such a weapon of mass destruction. And writing in Army and Navy Journal on Aug. 8, 1945, former President Herbert Hoover stated, “The use of the atomic bomb, with its indiscriminate killing of women and children, revolts my soul.”

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A presidential apology now would not excuse Pearl Harbor or exculpate Imperial Japan’s savage subjugation of Manchuria, Nanking and Korea during World War II. But if the long arc of the moral universe bends toward justice, then Obama must make amends for the horrific injustice perpetrated by Truman.

Rosario A. Iaconis, chairman of The Italic Institute, is an adjunct professor in the Social Sciences Department at Suffolk County Community College.