(CNN) Todd Vance was serving in the US Army when the September 11 attacks occurred.
"I decided to re-enlist for another three years," he said. "And I asked to be part of the first deployed unit to Iraq."
Vance served as a squad leader and ran more than 250 combat missions before returning to San Diego in 2005.
"At first, it was all elation. I was just happy to be alive and happy to be out of the military," he said. "Slowly but surely, reality was setting in about what I had seen and what I had done."