By Marissa Parra

CHICAGO (CBS) — Today we remember 9/11, but for U.S. service members, it’s a day that has a whole new meaning this year.

The Chicago Marines Foundation hosted a ruck march Saturday morning from the Loop to Wrigleyville, to honor the fallen and provide emotional support to veterans.

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CBS 2’s Marissa Parra reports they marched 13 miles along the lakefront for each of the 13 fallen Marines who died days before the end of the war in Afghanistan, which was prompted by the 9/11 terrorist attacks.

Sept. 11 is already a somber day that can be triggering for struggling veterans, so they likened Saturday’s march to “mobile therapy.”

For 13 miles, they carried the Marine Corps flag tall and proud, but the heaviest weight they carried was one you can’t see.

“I’m pretty emotional these days with a lot of stuff,” said Lisa Zychowski, who served in Afghanistan.

And for U.S. service members, this day can be a hard one to relive

“You think about the last 20 years,” said Joe Franzese, who served in the war in Iraq.

During the march, there’s a code, an understanding, that the person next to you gets what that really means.

“When we were singing the national anthem, I couldn’t stop crying, you know? I didn’t expect that, I didn’t know why,” veteran Matt Tune said.

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Emotions run high on a day loaded with meaning; the anniversary of a day of loss, and the day that would fuel America’s longest war, sending even some of these same marines into battle in Afghanistan.

But the end to the war that stretched on for 19 years and 8 months was a painful one.

“The questions arise. Was it worth it? I think that’s something that we’re struggling with,” Tune said.

“We all felt hopeless again,” said veteran Marc Okicich, with the Chicago Marines Foundation.

Okicich made some calls, and the sunrise ruck march was born:

“This is a therapy session. This is a 13-mile therapy session,” he said.

They carried the 13 names for the 13 fallen, and the weight of the day and the last two decades together

“We don’t have the answers, but we have each other,” Tune said.

Several veterans said the one message they want to leave people at home with is to reach out for help with mental health.

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You can call the Veterans Crisis Line at 800-273-8255.