Even after Dillon Behr was wounded, he kept fighting the enemy.

"I thought I was going to die," he said. But he never gave up.

Shot twice during a deadly ambush on a steep cliff in Afghanistan when he was a U.S. staff sergeant, Behr gives a harrowing account of the 2008 battle that changed his life in the "To Hell and Back" episode of National Geographic Channel's "No Man Left Behind" series. 

Premiering Tuesday, June 28, at 9/8c, the series combines gripping personal testimony with vivid re-enactments and archival footage to tell the stories of modern war heroes and special agents who overcame incredible odds in hostile environments.

Behr, a Green Beret, served in Iraq in 2005 and in Afghanistan in 2007. On April 6, 2008, during his second tour of Afghanistan, Behr was part of an American Special Forces mission to capture or kill the leader of the Hezb-e Islami Gulbuddin terrorist group.

The troops had to climb a mountain from the bottom of the Shok Valley up to a village.

"The enemy had the high ground,” Behr recalled. “They had built-in fortified positions. We were basically exposed climbing up this mountain.

The Americans were halfway to their target when they spotted combatants with rocket-propelled grenades, and they decided to engage them.

"It was the most intense firefight that I've ever been in,” Behr said. “A lot of bullets and RPGs and explosions. There were many more of them, and they were able to establish volume of fire superiority right away."

During the initial firefight, he said, the U.S. soldiers were forced beneath a tiny rock ledge. With bullets flying near his feet, Behr knew he had to find a safer position. He kept firing while trying to move, and "I was struck in the hip with a bullet … knocked on the ground."

The pain "was excruciating…. I often describe it as like being hit by a baseball bat by a professional baseball player.… it reverberated throughout my entire body."

Ron Shurer, a medic, rushed to his aid, and Behr was struck by another bullet that traveled through his right arm. Meanwhile, an Afghan interpreter was shot and killed. Other Americans were wounded, but none died that day. 

Behr's arm injury wasn't serious, but the wound to his pelvis caused severe blood loss.

But, even though he was hit, Behr fought on.

"I tried to do my best to ward off the enemy,” he said. “It was hard to really stay in the battle at that point, but I did do my part to help warn of potential dangerous scenarios and keep an eye out, because we were pretty much surrounded by the bad guys."

Shurer shielded Behr's body from American bombs that fell nearby, but a rock from one of the blasts hit Behr in the stomach. Later, doctors discovered that it had perforated his intestine.

"I actually thought that I was going to die and had made peace with it and felt like I was going to go to sleep and said to myself, 'All right, this is it.'

"And then Ron slapped me across the face and told me to wake up. That was the moment where it all turned around for me and I realized I wasn't going to die, at least not that moment, and decided to do what I could to get out of there."

After being evacuated by helicopter, Behr was whisked to a hospital in Afghanistan, where he said he died on the table.

"Looking at my medical records after the fact, I actually was coded out briefly. They resuscitated me," he said.

Before long he was back in the U.S., at the Walter Reed Army Medical Center, where doctors removed part of his small intestine and gave him a hip replacement.

"I'm not a legend,” says Behr, who has worked in intelligence and cybersecurity and who opened a non-profit gym for wounded veterans at Walter Reed after leaving the military. “The guys on the team that continued to battle while I was out, and that helped save my life and get us through that day … those guys are the legends."

That day in Afghanistan earned Behr the Silver Star and gave him "a new appreciation of just being alive."

American Legends – Stories of soldiers who responded to a difficult conflict situation, and did everything they could to defeat the enemy and get their brothers home.

"No Man Left Behind" premieres Tuesday, June 28 at 9/8c on the National Geographic Channel.

For more information and clips, visit natgeotv.com/NoManLeftBehind.