Both of his grandfathers fought in World War II, one in the Pacific, where the film takes place, and one in Germany.
"This was a dream for me to be able to do a film with that sort of content and these people," Phillippe told The Early Show co-anchor Harry Smith. "My grandfather was my hero. He won a Bronze Star in Germany. He would tell me stories, periodically, usually about mechanical things, tanks and guns, not about death and his friends dying next to him."
The movie tells the story of the famous Joe Rosenthal photo of five marines and one Navy corpsman raising a flag on Mount Suribachi in Iwo Jima. Three of the men who raised the flag die in the war, and the remaining three are brought back home to help raise money for the dwindling bond drive.
It turns out that the photo was not of the original flag raising. As the story goes, the first flag went up, but a commander wanted a bigger flag, which was raised by a different group of servicemen.
"(That) is something no one never knew and there were questions about the circumstances under which the photograph was taken," said Phillippe. "But the impact it had was phenomenal. They raised $25 billion in 1945 to win the war essentially. It galvanized the nation. We were out of ammo, out of equipment, out of uniforms and this bond drive paid for everything."
Phillippe says working for Eastwood was a dream come true.
"You hear the stories and the mythology, and it's all true," he said. "The guy is incredible. He's an amazing man. Look at him, 76 years old. He climbed the place we shot Suribachi. They had a helicopter that could have taken him up. The man is out there with two bags over his shoulders at 6 in the morning climbing this mountain. He's something else."
Phillippe is still pinching himself over this year's Oscar night. He was a member of the ensemble cast of "Crash," which one Best Picture while his wife, Reese Witherspoon, took home a Best Actress trophy for "Walk The Line."
"So surreal. I have little recollection of that night because of how overwhelmed I was in a sensory manner," he said. "It's almost dream-like."
The actor said he is working on another war-related movie, this time about a soldier back from Iraq.
"The men and women who make that sacrifice and are willing to give up their lives in a lot of cases are heroes to me," he said.