▶ Watch Video: Veteran bikes across U.S. to honor fallen soldiers

After four combat tours in Afghanistan, retired Army Col. Chris Kolenda wanted to honor his fellow soldiers. He went from not riding a bike in 20 years to riding 1,700 miles across the U.S. 

“I said to myself, ‘You know, I’m not getting any younger,'” he told CBS News. 

Kolenda biked across the country to visit the gravesites of the six fallen paratroopers from the unit he commanded. He has their names engraved on his bike. 

Since the attacks on Sept. 11, 2001, more than 7,000 U.S. service members have died in military operations related to the “Global War on Terror,” one study estimates. During that same time period, about four times as many — more than 30,000 active-duty service members and veterans — have died by suicide. 

“I feel a lot of gratitude for the service and sacrifice of our six fallen heroes. Gratitude for the 800 who had my back for 15 months,” he said. 

Combat changed the survivors, with many struggling with post-traumatic stress disorder. 

“One of our paratroopers, he now lives in a dumpster. He’s a meth addict,” Kolenda said. “In our unit alone, we’ve lost more to suicide and substance abuse than enemy fire. We had one of our paratroopers die two weeks ago by suicide.” 

Kolenda said those who ask veterans about their service should keep it positive. 

“What was the best experience you ever had? What was the most awesome thing about your service?” were the types of questions he suggested. “Very positive questions.” 

The chaotic end of the U.S. war in Afghanistan also triggered emotions for Kolenda.

“Over 2,300 service members killed, to include six of my own, from my own unit. Tens of thousands wounded, $2 trillion spent, 20 years. And to see it all come crashing down like a house of cards, I was very angry,” he said. 

He put the emotions into that bike ride, scaling a steep, four-mile hill in Pennsylvania to visit the grave of Capt. Dave Boris. 

“I don’t think I ever gave myself the permission, the room to grieve for him,” Kolenda said. “I’m imagining Dave next to me. Of course, he would have beat me up that mountain. He would have been taunting me the whole way.”

On that 1,700-mile journey, Kolenda learned that sometimes you’ve got to open old wounds to heal better. 

If you or someone you know is in emotional distress or suicidal crisis, call the National Suicide Prevention Hotline at 1-800-273-TALK (8255).

For more information about mental health care resources and support, The National Alliance on Mental Illness (NAMI) HelpLine can be reached Monday through Friday, 10 a.m.–6 p.m. ET, at 1-800-950-NAMI (6264) or email [email protected].