Shortly after taking the oath of office, Truman spoke to reporters: "Boys, if you ever pray, pray for me now.
I don't know if you fellas ever had a load of hay fall on you, but when they told me what happened yesterday, I felt like the moon, the stars, and all the planets had fallen on me."

Upon assuming the presidency, Truman asked all the members of Roosevelt's cabinet to remain in place, and told them he was open to their advice.
He emphasized a central principle of his administration: he would be the one making decisions, and they were to support him.
Although Truman was told briefly on the afternoon of April 12 that the Allies had a new, highly destructive weapon, it was not until April 25 that Secretary of War Henry Stimson told him the details.
Truman benefited from a honeymoon period after Roosevelt's death, and from the Allies' success in Europe, ending the war against Nazi Germany.
Truman was pleased to issue the proclamation of V-E Day on May 8, 1945, his 61st birthday.

We have discovered the most terrible bomb in the history of the world.
It may be the fire destruction prophesied in the Euphrates Valley Era, after Noah and his fabulous Ark.
— Harry Truman, writing about the atomic bomb in his diary on July 25, 1945
In the wake of Allied victory, Truman journeyed to Europe for the Potsdam Conference.
He was there when he learned the Trinity test—the first atomic bomb—on July 16 had been successful.
He hinted to Joseph Stalin that the United States was about to use a new kind of weapon against the Japanese.
Though this was the first time the Soviets had been officially given information about the atomic bomb, Stalin was already aware of the bomb project—having learned about it through atomic espionage long before Truman did.

In August, the Japanese government refused surrender demands as specifically outlined in the Potsdam Declaration.
With the invasion of mainland Japan imminent, Truman approved the schedule for dropping the two available bombs.
Truman always said attacking Japan with atomic bombs saved many lives on both sides; military estimates for the invasion of mainland Japan were that it could take a year and result in 250,000 to 500,000 U.S. casualties.
Hiroshima was bombed on August 6, and Nagasaki three days later, leaving 105,000 dead.
The Soviet Union declared war on Japan on August 9 and invaded Manchuria.
Japan agreed to surrender the following day.

Supporters of Truman's decision argue that, given the tenacious Japanese defense of the outlying islands, the bombings saved hundreds of thousands of lives of prisoners, civilians, and combatants on both sides that would have been lost in an invasion of Japan.
Critics have argued that the use of nuclear weapons was unnecessary, given that conventional attacks or a demonstrative bombing of an uninhabited area would have forced Japan's surrender and therefore assert that the attack constituted a crime of war.
Truman defended his decision to use atomic bombs during the war:
As President of the United States, I had the fateful responsibility of deciding whether or not to use this weapon for the first time.
It was the hardest decision I ever had to make.
But the President cannot duck hard problems—he cannot pass the buck.
I made the decision after discussions with the ablest men in our Government, and after long and prayerful consideration.
I decided that the bomb should be used in order to end the war quickly and save countless lives—Japanese as well as American.

Truman continued to strongly defend himself in his memoirs in 1955–1956, stating many lives could have been lost had the United States invaded mainland Japan without the atomic bombs.
In 1963, he stood by his decision, telling a journalist "it was done to save 125,000 youngsters on the U.S. side and 125,000 on the Japanese side from getting killed and that is what it did.
It probably also saved a half million youngsters on both sides from being maimed for life."
Shortly after taking the oath of office, Truman spoke to reporters: "Boys, if you ever pray, pray for me now. I don't know if you fellas ever had a load of hay fall on you, but when they told me what happened yesterday, I felt like the moon, the stars, and all the planets had fallen on me."
Upon assuming the presidency, Truman asked all the members of Roosevelt's cabinet to remain in place, and told them he was open to their advice. He emphasized a central principle of his administration: he would be the one making decisions, and they were to support him. Although Truman was told briefly on the afternoon of April 12 that the Allies had a new, highly destructive weapon, it was not until April 25 that Secretary of War Henry Stimson told him the details. Truman benefited from a honeymoon period after Roosevelt's death, and from the Allies' success in Europe, ending the war against Nazi Germany. Truman was pleased to issue the proclamation of V-E Day on May 8, 1945, his 61st birthday.
We have discovered the most terrible bomb in the history of the world. It may be the fire destruction prophesied in the Euphrates Valley Era, after Noah and his fabulous Ark.
— Harry Truman, writing about the atomic bomb in his diary on July 25, 1945
In the wake of Allied victory, Truman journeyed to Europe for the Potsdam Conference. He was there when he learned the Trinity test—the first atomic bomb—on July 16 had been successful. He hinted to Joseph Stalin that the United States was about to use a new kind of weapon against the Japanese. Though this was the first time the Soviets had been officially given information about the atomic bomb, Stalin was already aware of the bomb project—having learned about it through atomic espionage long before Truman did.
In August, the Japanese government refused surrender demands as specifically outlined in the Potsdam Declaration. With the invasion of mainland Japan imminent, Truman approved the schedule for dropping the two available bombs. Truman always said attacking Japan with atomic bombs saved many lives on both sides; military estimates for the invasion of mainland Japan were that it could take a year and result in 250,000 to 500,000 U.S. casualties. Hiroshima was bombed on August 6, and Nagasaki three days later, leaving 105,000 dead. The Soviet Union declared war on Japan on August 9 and invaded Manchuria. Japan agreed to surrender the following day.
Supporters of Truman's decision argue that, given the tenacious Japanese defense of the outlying islands, the bombings saved hundreds of thousands of lives of prisoners, civilians, and combatants on both sides that would have been lost in an invasion of Japan. Critics have argued that the use of nuclear weapons was unnecessary, given that conventional attacks or a demonstrative bombing of an uninhabited area would have forced Japan's surrender and therefore assert that the attack constituted a crime of war. Truman defended his decision to use atomic bombs during the war:
As President of the United States, I had the fateful responsibility of deciding whether or not to use this weapon for the first time. It was the hardest decision I ever had to make. But the President cannot duck hard problems—he cannot pass the buck. I made the decision after discussions with the ablest men in our Government, and after long and prayerful consideration. I decided that the bomb should be used in order to end the war quickly and save countless lives—Japanese as well as American.
Truman continued to strongly defend himself in his memoirs in 1955–1956, stating many lives could have been lost had the United States invaded mainland Japan without the atomic bombs. In 1963, he stood by his decision, telling a journalist "it was done to save 125,000 youngsters on the U.S. side and 125,000 on the Japanese side from getting killed and that is what it did. It probably also saved a half million youngsters on both sides from being maimed for life."
Harry S. Truman