The grandson of former U.S. president Harry Truman says his grandfather expressed regret over the loss of life in Japan, the site of the world’s first atomic bombing.

“He made the decision to end the war and save American lives, save Japanese lives, but he always regretted the loss of life in Hiroshima and Nagasaki,” Clifton Daniel told CTV’s Canada AM on Friday.

Daniel was not yet born when the U.S. dropped an atomic bomb on Hiroshima and Nagasaki in August, 1945, killing tens of thousands of people.

Daniel’s grandfather, then-U.S. president Harry Truman, ultimately made the call to drop the bombs, in a bid to stave off further American war casualties and force Japan to surrender.

On Friday, nearly 71 years after the deadly nuclear attack, Barack Obama became the first sitting U.S. president to visit Hiroshima.

Daniel said like his schoolmates, he learned about the bombing in school.

“My grandfather never spoke to me about them,” Daniel said. “To be fair, I never asked.”

But Daniel said that his grandfather carried the weight of his decision to drop the bomb throughout his life.

He spoke about it both privately and publicly, his grandson said, expressing that he “made the decision to end the war and save American lives, save Japanese lives, but he always regretted the loss of life in Hiroshima and Nagasaki.

“The loss of women and children, as he put it.”

Years ago, Daniel visited Hiroshima and Nagasaki to honour the victims of the attacks.

“When my family and I went four years ago, we were really feeling our way along, trying to find the balance,” Truman Daniel said. “We fielded questions about apology.”

During his historic visit to Hiroshima on Friday, Obama paid tribute to the victims of the bomb and urged nations to put an end to nuclear weapons stockpiling. He stopped short of formally apologizing for the nuclear attack, which many Americans view as a justified means to end the war.

Daniel said Obama did the “right thing,” by honouring the victims of Hiroshima and Nagasaki while also “remembering the sacrifices of that war and remembering the heroism of American troops and Canadian troops.

“It’s a tough call, I thought he did a good job,” Daniel said.