The Real-Life Heroes Behind '13 Hours: The Secret Soldiers of Benghazi'

— -- What happened during the 2012 Benghazi attack is the most scrutinized, most politically explosive “13 Hours” in recent history, and now the real-life American commandos who fought that night are coming forward to share their stories.

On Sept. 11, 2012, Ansar l-Sharia armed militants attacked a U.S. diplomatic compound and then a CIA annex in Benghazi, Libya, killing four Americans, including U.S. Ambassador Chris Stevens. Mark “Oz” Geist was one of the six former elite military operatives who fought back that night.

"We knew to get out of there we were going to have to depend on each other, kill them before they kill you," he told "Nightline."

Former Army Ranger Kris “Tonto” Paronto and former Marine Sgt. John “Tig” Tiegen were also there.

"That night was simply chaotic, not just a simple firefight and then we all got to go home," Paronto said.

Michael Bay directed "13 Hours," the so-called "Secret Soldiers of Benghazi" version of what happened. The movie is based on a book co-written by Geist, Paronto and Tiegen and other former elite operatives hired as security contractors to guard the Benghazi compound.

"It was a really heroic night," Bay said. "I never knew that until I read the book and talk to these guys."

In real-life, the tragedy triggered massive investigations. At its core, questions of insufficient security and what then-Secretary of State Hillary Clinton did and didn't know. Yet after 70,000 pages of documents , 32 hours of hearings -- longer than Congress took to investigate the 9/11 attacks -- Benghazi has become synonymous with partisan sniping and the movie is already re-igniting a firestorm in the midst of a heated presidential race.

At Thursday night’s debate, Republicans pounced on Clinton.

“Someone who lies to the families of those four victims in Benghazi can never be president of the United States,” Florida Sen. Mark Rubio said.

But while many of Clinton's enemies use Benghazi to hold her accountable, Geist has his own perspective.

“Do I hold her accountable? No. You know who I hold accountable is al-Sharia,” he said. “That’s who attacked them. That’s who killed the ambassador.”

John Krasinski plays Jack Silva, an alias for another one of the contractors guarding the annex when the diplomatic compound came under attack.

“There's a big disconnect if everybody thinks they know about Benghazi and they've never even heard the actual story of what happened that night,” Krasinski said. "For me, the most important thing that I hope people are surprised by is how little, if any, politics are involved in the movie."

At 9:42 p.m. on Sept. 11, 2012, the security team got a call that Stevens’ security team needed help. The men geared-up, raring to race to the rescue, but the CIA base chief -- in the movie version -- delays them. This is one of the biggest points of contention.

While congressional reports say that didn’t happen, the men say the crucial delay, about 20 minutes, crippled their rescue mission.

“It cost the lives of Sean Smith and Ambassador Stevens,” Tiegen said. “He said, ‘stand down, you need to wait.’”

“He told me to wait twice,” Paronto said. “We can get into semantics but ‘stand down’ was said … credit to the movie that they believed what we were saying and they put it in the movie.”

In a statement to ABC News, the CIA called the claims in the movie "shameful," "a distortion of events" and denied that a “stand down” order was given.

“No one will mistake this movie for a documentary," the statement continued. "It’s a distortion of the events and people who served in Benghazi that night. It’s shameful that, in order to highlight the heroism of some, those responsible for the movie felt the need to denigrate the courage of other Americans who served in harm’s way.”

Congressional committees have been told CIA officials were trying to protect the rescue team and waited to team up with local militias. The base chief told The Washington Post on Friday that "at no time did I ever second-guess that the team would depart.”

Tiegen said that by the time they got to the compound, the extremists had set fire to the residence with the ambassador inside.

“It's an extreme intense heat. It's like being in like … walking into a brick oven. It's like so hot. You instantly start sweating. The smoke is so thick and black,” he said. “It was just you couldn't even see the end of the barrel of the weapon with the flashlight on.”

Tiegen suffered lung damage from repeatedly diving back into the black smoke and flames. It’s a scene Krasinski re-lived on set.

“You do kick into a primal, very instinctual place where you're not thinking about acting or what you look like on camera,” he said. “Your body starts to do weird things. You tense up. You become hyper-focused and you become aware of every tiny opening of safety that you can find.”

The team couldn't locate Stevens but rescued his security detail, who were separated during the fire. Eventually, they returned to defend the CIA annex where they encountered repeated heavy fire.

"You risk your lives for anyone that needs help," Paronto said. "That's where the difference is where people understand that we are going to give our lives. We are going to risk our lives for others if you need us to do it. That how we're bred, raised."

The men took to the rooftops holding down the militants until one final deadly barrage. Geist’s arm was badly mangled by mortar fire. Even with his arm nearly severed, he tried to return fire.

“I start firing and I change magazines and as I'm coming back up that's when the first mortar hits the roof and takes out my arm,” he said.

By dawn, Stevens was pronounced dead from smoke inhalation. Former Navy SEAL Tyrone Woods and former Marine Glenn Dougherty were both killed in action. But the team managed to rescue about 30 other workers.

The State Department later admitted the Benghazi outpost was "woefully" under secured. Though Clinton is not mentioned in the movie, she had to answer questions repeatedly about the motivations of the attackers during 11 hours of congressional testimony last year.

Later, congressional investigations concluded that while fighter jets and tactical teams were scrambled from the nearest bases, they were too far away to get there in time.

When asked if he thought the U.S. military let him down, Paronto said “we don’t want to get into that.”

“We want to tell what happened on the ground and really honor the courage that was taking place,” he said. “We’ll let other people deal with those issues.”

Geist is still living with the aftermath of that night. After 14 surgeries, his hand is still badly mangled.

“I’ve got limited feeling in the palm of my hand and I don't have much dexterity with it, but I mean it’s attached and it works,” he said.

Bay, known for his movies "Transformers" and "Armageddon," said he was drawn to the story of unsung heroes.

"The extraordinary thing about this story, they did not have to go," he said. "When they heard the RPGs and AK-fire they volunteered."

The stadium premiere, with 30,000 fans, is donating proceeds to multiple organizations including the “Shadow Warriors Project,” a group proving medical care for wounded contractors.

"Once we get injured and we get out of contract, we get no more pay," Tiegen said. "I got a lot of lung damage when I was over there trying to get care through the workman’s comp and it just wasn't working."

When asked what he says to critics who claim telling his story is politically motivated, Geist said "that’s the problem."

"We as a country have gotten politicized or so polarized," he said. "This is something that I think was done right down the middle... you’ve got honor, you’ve got integrity, you’ve got courage because that is what we need and I hope people come to see this, to bring it back to the center."

ABC News' Ely Brown and Justin Fishel contributed to this report