The Invictus Games, a sports competition for wounded veterans created by Britain's Prince Harry, are underway in Toronto.

More than 500 athletes hailing from 17 different countries are there to compete in 12 events.

Many eyes are on Prince Harry, who made his first public appearance with American girlfriend Meghan Markle (who lives in Toronto) at the opening of this year's games over the weekend.

At Saturday's opening ceremony, sitting alongside first lady Melania Trump, and making his first public appearance with his girlfriend (though sitting four rows apart), Prince Harry's presence directed much of the attention.

But it's the wounded athletes on the field who are commanding the spotlight, like U.S. Air Force Master Sergeant Ben Seekell.

"There are some world-class athletes out there," he told CBS News correspondent Jeff Glor. "So I'm gonna have to put my best foot forward, if you will, and get out there and do what I trained to do."

While working as a dog handler in Afghanistan in 2011, Sgt. Seekell and his canine partner, Charlie, encountered a landmine just outside their base.

"Time seemed to slow down," he said. "That's the one thing that the movies might get right sometimes."

Charlie wasn't seriously hurt, but Sgt. Seekell lost the lower portion of his left leg. "For me, the choice was simple. I had a goal: I wanted to walk, I wanted to run, I wanted to do everything. And the only way to get there was to get up and go."

Still on active duty, Sgt. Seekell is looking to add to the three medals he won at the Invictus Games last year. "My expectations for myself are high," he said. "I'm not willing to walk away from the field with anything less than gold."

Sebastiana Lopez Arellano, part of the U.S. Wheelchair Rugby team, is defending gold at this year's Invictus Games. CBS News

Retired Air Force Staff Sgt. Sebastiana Lopez Arellano is also defending gold, as the only woman on the U.S. Wheelchair Rugby team.

"I ain't scared of those boys," she said. "What are they going to do, flip me? Bring it!"

Lopez Arellano was injured riding a motorcycle off-duty. She lost most of her right leg. Recovery required about two years at Walter Reed.

"I was in a coma for about, I don't know, 36 days or something like that. And when I woke up I was so happy, I was like, Oh cool, I'm alive, because I thought I died."

Aaron Moffet, a sports psychologist and the head coach of Team USA, told Glor, "So many of them come from literally off the couch.

"What we want to do is make this part of their everyday life," he said. "We don't want them just be active one day a year. We want them to be active 365 days a year."

The Invictus Games run through Saturday.