If in the past couple of days you've been anywhere between Spicer in Kandiyohi County and Plymouth in the Twin Cities' western suburbs, perhaps you've seen them: Three military veterans carrying huge rucksacks and a banner.

"VETS HAVE EACH OTHERS' BACKS," the banner reads.

The three veterans embarked Friday on the 100-mile ruck to raise money for Project Got Your Back, a nonprofit that connects Minnesota military veterans with other vets for yearlong mentorship relationships to help navigate the often arcane and complex world of veterans' benefits, resources and networks.

They'll continue rucking along the Luce Line State Trail on Sunday, carrying their stuffed rucksacks and pitching tents to sleep along the way, before finishing Monday evening at Luce Line Brewing Co. in Plymouth.

"There's so many things out there for veterans," said Paul Davis, a 33-year-old Marine Corps veteran from St. Michael who organized the fundraiser. "We connect the unconnected. There's this whole world of companies and organizations and programs and people who just want to help. At last count there were 380 just within Minnesota alone designed to help with vets: from PTSD and homelessness to things like free wakeboarding trips to Lake Tahoe for veterans, or $500 checks from the Minnesota Military Appreciation Fund. There's so much out there that vets don't know about, and it's gut-wrenching to see that gap."

When Davis wanted to raise awareness and funds for the organization, formerly known as the Veteran Small Business Foundation, he figured a four-day ruck with two veteran friends, Rick Stephas and Evan Workman, would do the trick.

Exhausting hikes with 80-pound rucksacks are a fixture of basic training. It's not something they'd necessarily enjoy, but it's something that brings vets together and tests their will.

"We all have felt the pain of a ruck before," said Stephas, who served in the same Marine unit as Davis and now lives outside Sioux City, Iowa. "I'm going to be a 36-year-old man with sore joints and backaches. Why would I do it? It's fulfilling. I joined the service because I wanted to do something. When you get out of the Marine Corps, you kind of lose that. You don't get that in everyday civilian life. I go to work, raise kids, have a wife — life is good. But what in life actually challenges you? This does that, and it benefits others."

Davis works in Boston Scientific's materials management group, where daily rucks aren't exactly part of the workday. He's put himself back in training the past few months. One of the ways he's prepared has been to put a big paver beneath his work desk. He's most worried about his feet — sores and blisters and the like — so he has been mashing them on the paver for eight hours a day, strengthening his skin and building up calluses.

The vets are doing the ruck in true Marine Corps fashion. Davis put together an operation order. The Luce Line State Trail is 63 miles, not 100, so they hiked from Spicer to Cosmos on the first day just to get to the trailhead. Davis added a few turns to lengthen the route — he mapped it to 101 miles on Google Earth — and picked stops along the way to pitch tents and hammocks.

If you do spot the veterans on their hike, be sure to look down at Davis' feet. He could have picked more comfortable footwear, but instead opted for boots he's intimately familiar with — worn-in all-terrain boots he got in 2012, before he deployed to Afghanistan. For seven months, he wore those boots in Helmand Province.

"It's a great symbol and reminder along the way," Davis said. "Marines love hardship and pain. What could be better than 100 miles of hardship and pain?"

Reid Forgrave • 612-673-4647