Creative license is a Hollywood norm, but when actor Michael Kelly had to ask the real-life Army officer he portrays in The Long Road Home, Lt. Gen. Gary Volesky, for a few clarifying details about the war in Iraq, he ended up betraying the show's writer's room.

“Volesky was like, ‘Wait a minute, you keep me asking questions about the [command center]. I wasn't there that much,” Kelly recalls the general telling him. “So I had a little bit of explaining to do."

As it turned out, the writers of The Long Road Home had "merged" parts of Volesky’s backstory with that of another commander, Capt. George Lewis, for the sake of cinematic consistency. As for the "merger"? "We had a good laugh about it," Kelly says. "He's such a great, understanding man. He's got it all."

Kelly, the veteran actor perhaps best known as the ruthless and loyal chief of staff Doug Stamper on the Netflix hit House of Cards, brilliantly portrays the decorated war hero on Nat Geo’s acclaimed eight-hour war miniseries. In this week’s episode—catch the preview above—Volesky must lead three convoys to rescue the ambushed First Cavalry Division out of Sadr City, Iraq, on April 4, 2004. While his own Humvee is coming under fire, it’s Volesky’s responsibility to calmly divert the other convoys from coming in, thereby saving countless lives.

“In the research that I did about Lt. Gen. Volesky, I realized that as a leader, you have to remain calm and in control," Kelly said. "If you're not, and you convey to your men that you're erratic, that [panic] is gonna spread like wildfire. So it starts from the top. Being the leader that he was, he knew that if he stayed calm, his men would stay calm, and that was the best chance of survival.”

Besides the character preparation, there were the physical demands of portraying a military giant. While Kelly has run a marathon in the past, simulated weapons training was an entirely new type of hurt on Kelly’s 48-year-old body. “I consider myself to be in pretty good shape,” he says. “But by the third day, my right shoulder had the worst pain. One of the advisers told me, ‘That's your rifle shoulder—your rifle muscle. It was that type of good workout, you know, that when you finish at the end of the day, you can't wait to go back to base and fry up the barbecue and crack a cold beer.”

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At home, the pathway along New York’s East River is Kelly’s training grounds, where you’ll find the actor running a few times a week during the warmer months with his wife, Karyn, a personal trainer. When the temperature drops, and the winds swirl, those plans may be diverted indoors. "My wife and I joke that every time you run on the river, you're like: 'How does the wind blow in your face going north and blow in your face when you turn around and run south?'" Kelly says.

Looking back, Kelly says he feels honored to portray the real-life hero. Initially, though, he nearly turned down the part due to a scheduling conflict. But more research into Volesky and the heroism displayed during "Black Sunday," as that operation became known, made it impossible to pass up. "The more I learned about the sacrifices that he made in real life, I was like, 'I’m gonna make this work into my schedule.'" The decision paid off. The show has debuted to critical acclaim, and Kelly met the commander—even if only for less than an hour.

"He was just so incredibly informative," Kelly says. "Everything I had read and learned about the man is exactly the way he was, and I was incredibly grateful for not only the time he spent but also [the chance] to learn that he was what I thought he was."

Nat Geo’s The Long Road Home airs Tuesdays at 10/9c.