When Army veteran Stephen Simmons returned from his last tour in Iraq in 2008, post-traumatic stress disorder made it difficult for him to adapt to civilian life.

But he's found comfort in his pets and in exploring the great outdoors, and he's now working to improve the lives of other veterans suffering from PTSD.

After a friend suggested he try adventure therapy, Simmons moved from Bluefield, West Virginia, to Grants Pass, Oregon, in 2012.

"Adventure Therapy is about using the symptoms of PTSD in a positive way," he said. "Instead of ignoring and repressing aggressive tendencies or jolts of adrenaline in your system, you can put them to work by challenging yourself against nature. It’s about action rather than apathy."

Simmons made the cross-country move with just his Jeep and his dog, Puppi, whom he'd found atop a mountain in 2004.

When Simmons returned from war, Puppi was certified as his service dog, and since then, his dog has "never wanted to be more than 10 feet away from me," he told Purina.

He believes that Puppi absorbs his emotions and shares in both his happiness and his depression. He says this empathy helps him heal.

Simmons and Puppi lived out of the Jeep, exploring the wilderness by day and sleeping in the car at night.

One evening, Simmons decided to climb Mount McGlouhlin, a 9,000-foot volcano, with Puppi.

"I didn't really know what I was getting into, but it was my first foray into adventure therapy. Looking back, I was reckless and ill-prepared, but Puppi and I climbed that mountain."

Simmons and his dog made the climb through snow, and as he struggled to maintain his footing, he had a realization.

"I realized that I cared a lot more about what happened to me than I thought I did. There's something about balancing on the slope of a mountain, pumped full of adrenalin, and close to the top."

Burma the adventure cat

A self-described animal lover who once rescued a cat in Iraq, Simmons couldn't resist adopting a tiny brown cat, when he met a teenage girl with a box of kittens outside an Oregon grocery store.

He adopted the kitten and named her Burma.

Burma the adventure cat on a mountainSimmons often brought Burma along on his hikes in a pet carrier before letting her out to hike flatter parts of the trail. The cat proved to be just as adventurous as Simmons and Puppi, scaling rocks and even swimming in lakes.

"He really has become part of the group, and he’s totally comfortable hiking, swimming, and climbing mountains with us," Simmons said.

But Burma was more than just another four-legged hiking companion. She also proved to be quite the conversation starter on the trail, forcing Simmons outside his comfort zone and helping him to connect with fellow hikers.

Throughout their journey, Simmons documented his pets with his camera phone and posted the pictures to social media. Burma has become especially popular, accruing thousands of Instagram followers.

When Simmons' friend, Lydia Davey, a Marine veteran, saw his photos, she suggested he create a book. Together, they started a Kickstarter campaign and raised more than $14,000 to create a picture book titled "The Adventures of Puppi and Burma."

His second book, "Burma: Adventure Cat" is slated for publication this fall.

Simmons hopes the books and his story will help others who suffer from PTSD.

"The biggest lesson that I've learned in the last couple of years is that no matter how dark it seems … that hopelessness — it's a lie. It's something that's hijacked your life, and the real person that you were is still there."

But Simmons says he couldn't have learned this valuable lesson without the love and companionship of Puppi and Burma.

"Aside from providing unconditional love, and making the sights, sounds and smells of the wilderness more meaningful, Puppi and Burma are a responsibility," he told the Huffington Post. "I care for them as much as or more than I care for myself. During especially difficult times, I would not have gotten up or gone out for myself, but I would do it for them. Puppi and Burma have been a blessing in every way."

Meet Simmons and his furry friends in the video below.

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Inset photo: BurmaAdventureCat/Instagram