Private Desmond Doss walked into the bloodiest battle of World War II’s Pacific theater with nothing to protect himself save for his Bible and his faith in God. A devout Seventh Day Adventist and conscientious objector, Doss had enlisted as a medic and refused to carry a rifle.

The fighting took place on the hellish Maeda Escarpment in April 1945. The battlefield, located on top of a sheer 400-foot cliff, was fortified with a deadly network of Japanese machine gun nests and booby traps. The escarpment, nicknamed Hacksaw Ridge for the treacherously steep cliff, was key to winning the battle of Okinawa. The mission was thought to be near-impossible, and when Doss’s battalion was ordered to retreat, the medic refused to leave his fallen comrades behind.

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Facing heavy machine gun and artillery fire, Doss repeatedly ran alone into the kill zone, carrying wounded soldiers to the edge of the cliff and singlehandedly lowering them down to safety. Each time he saved a man’s life, Doss prayed out loud, “Lord, please help me get one more.” By the end of the night he had rescued an estimated 75 men. (The always modest Doss reckoned he saved about 50, but his fellow soldiers gauged it closer to 100. They decided to split the difference.)

The unbelievable story has come to life in the Mel Gibson-directed Hacksaw Ridge, with Andrew Garfield starring as Doss. The film earning a 10-minute standing ovation at its red carpet world premiere at the Venice Film Festival in September.

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Doss never lived to see his story on the big screen. He died in 2006, and while he spent much of his later life retelling the incredible events of that night, he was always reluctant to trust Hollywood with his story. “I grew up in a house where there was an endless stream of people coming through the door wanting to make a movie, write a book, etc,” Doss’s only child, Desmond Jr., tells PEOPLE. “The reason he declined is that none of them adhered to his one requirement: that it be accurate. And I find it remarkable, the level of accuracy in adhering to the principal of the story in this movie.”

“[Mel Gibson and I] were very accurate with Desmond and what happened to him,” veteran producer Bill Mechanic tells PEOPLE. But, he admits “we were not accurate on some of the details around it,” like the exact backstory of Doss’s father, or the chronological details of his marriage to his wife, Dorothy. “If you’re a slave to the complete facts, than you’re not making a movie that is compelling,” argues Mechanic.

Minor embellishments aside, the filmhas been both celebrated and criticized for its gritty realism, which includes close-ups of everything from spurting arteries to rats feeding on human entrails. “Oh yes, it was graphic,” said Joe Clapper, a 95-year-old Okinawa veteran tells PEOPLE of the film. “But when you’ve been there, that’s what it’s like.”

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“Okinawa was the bloodiest battle of the Pacific and the second most bloody battle of World War II,” adds Mechanic. “Doss was also a medic, so it’s not like you can just show soldiers getting shot next to him — you have to see what he’s working on. You have to put him in hell essentially before you can see the decisions that he made and who he was, how strong his faith was and how courageous he was.”

Doss’s faith and courage were forged growing up in Lynchberg, Va., the middle child of William Doss, a carpenter and WWI veteran, and Bertha Doss, a homemaker. As depicted in the movie, young Doss was captivated by a framed poster of the Ten Commandments hanging in his childhood home. He was particularly intrigued by a illustration of the Sixth Commandment, showing Cain murdering his brother Abel. His father, played by Hugo Weaving in the movie, suffered from alcoholism and depression relating to the PTSD he suffered in the war. In the movie, a young Doss wrestles a gun out of his father’s hand during a fight between his parents. The scene draws on a real event in Doss’s life, in which a fight between his father and uncle made him swear off guns.

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When the Japanese attacked Pearl Harbor, Doss was working at a shipyard in Newport News. His position made him eligible for deferment, but despite his inherent pacifism, Doss felt a moral obligation to fight for his country. He hoped that by joining the army as a medic, he could avoid carrying a weapon, and even believed he might be allowed to rest in honor of the Sabbath on Saturdays.

While Doss viewed himself not as a conscientious objector, but a conscientious cooperator, his fellow infantrymen and superiors did not see it that way. When he arrived for basic training at Fort Jackson, S.C., he quickly became an outcast from the rest of the recruits. His slight stature and shyness did not improve the situation, and many soldiers believed he would be a major liability in battle. As shown in the film, Doss was subjected to physical and psychological abuse, and endured several attempts by his superiors to have him discharged from the military.

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Undeterred, Doss deployed with the 307th Infantry, 77th Infantry Division, in the summer of 1944. While not depicted in the movie, he served as a medic on Guam and in the Philippines prior to the Battle of Okinawa. During that battle, Doss sprinted through heavy enemy fire to save his fellow soldiers. The danger was even greater for Doss as the Japanese often targeted medics. He ended up serving for two more weeks before being wounded by shrapnel from a grenade. Despite his injuries, he continued to treat other soldiers until his arm was broken by Japanese fire.

President Harry S. Truman presented Doss with the Medal of Honor on Oct. 12, 1945. He was the first conscientious objector to receive the honor. He spent the first five years after the war recovering from his injuries, and ultimately lost a lung to tuberculosis. His injuries prevented him working full-time, and he devoted the rest of his life to working with his church.

Growing up as Doss’s son, Desmond Jr. says he heard the tale of his father’s heroics many times. Despite knowing the story’s facts, Desmond Jr. says he does recall asking his father a personal question about that night. “What on Earth were you thinking?” he says with a laugh. “And I never really got the answer I was looking for. Even at a very private, intimate level, he just wanted to give all the glory to God and never seemed to acknowledge his role.” Still, Desmond Jr remembers wanting to ask, “Did he not understand that it’s not right to stand up in the middle of a hail fire of bullets?”

Doss was happy to speak about the battle with church groups and audiences all over the country, but Desmond Jr. says the scars from the war never faded. “The war is never over and it was the same thing with my dad. It went on and on and on, and even after he’s dead it’s still going on now with this movie,” he explains, adding, “How can the war be over for you when you’re missing an arm, or missing an eye? How does your family relate when they send you off and you come back in a wheelchair. It’s just never over.”

But Desmond Jr. takes solace in the lives his father saved, and while he hardly ever hears from the survivors, he knows there are entire families that might not exist without his dad. “I did see on Facebook recently that someone had written that their grandfather wouldn’t be alive without my dad saving them. So there is that connection,” he recalls. “Something swirls up in you to think that someone you’re close with made such a difference in people’s lives. It’s very heartwarming.”