- Before starring in "Oppenheimer," Matt Damon said he spoke to Ben Affleck's Marine vet grandfather.
- Damon said Affleck's grandfather told him he cheered when the US dropped atomic bombs on Japan.
Matt Damon said he spoke to Ben Affleck's grandfather who served in World War II about Hiroshima before starring in "Oppenheimer."
During a chat with CNN's Chris Wallace, who wrote "Countdown 1945," a book on the 116 days leading up to Hiroshima, Damon, 52, was asked to weigh in on the US's decision to drop atomic bombs on Hiroshima and Nagasaki — events that led to the deaths of over 200,000 people in August 1945.
In the interview, some of which was shared by Mediaite, Wallace and Damon discussed how some members of the US government and military thought that the atomic bomb would help bring the war to an end.
Whether that was right or wrong given the circumstances is "an impossible question," Damon said.
"I remember talking to Ben Affleck's grandfather who was a Marine," he said. "And he said, 'When we heard about the bomb dropped, we cheered.'"
"This is 50 years later, he's telling you this and he goes, I you know, I live with the fact that I cheered," he said. "But this is what they were telling us, you know, that they were going to fight to the last man."
Damon added that if he had been involved in the decision at the time, he likely would've had a "head of gray hair."
In "Oppenheimer," Damon plays General Leslie Groves, a US Army officer who led the development of nuclear weapons in the US, an operation code named the Manhattan Project.
For his part, Damon said he didn't think Groves "ever lost a night of sleep" about the bombings as he "fulfilled his mission."
The same cannot be said for J. Robert Oppenheimer, the scientist known as the "father of the atomic bomb," and some of his colleagues, the actor added.
"Once they went through the test, you know, they started going 'Oh my god," he said. "It was like it was like a shockwave going through them."