What's your "why?" Mark Goldman's "why" for being an Ironman is simple. "I can because they can't."

They are the 13 Americans the Ironman athlete competes in honor of in the 13 for 13 Heroes Mission.

Goldman said, "13 for 13 Heroes is simply a mission to complete 13 Ironman, full distance or half distance races in honor of each of the 13 service members who we lost on August 26th of withdrawing from Afghanistan after our 20-year presence there."

Goldman is a husband, father and businessman from Minneapolis. He's a recreational athlete who turned to Ironman racing to test his personal limits and improve his health.

The Ironman is a 140.6-mile endurance race featuring a 2.4-mile swim, 112 miles of cycling and a 26.2-mile run.

The explosion that took the lives of the 13 service members at the Kabul Airport made Goldman think his athletic efforts could bring attention to the sacrifice military families make.

Each of his races takes place near where one of the heroes grew up. Goldman races with an American flag tucked into his wetsuit, his bike jersey pocket and on a flag pole he carries while he runs the marathon.

Goldman's mission will be spread out over three years.

Race number 4 is Ironman Sacramento where Goldman will honor the life of Marine Sgt. Nicole Gee, who grew up in Roseville.

Sherri Juels, Gee's aunt, will be at the race cheering Goldman on and will greet him at the finish line. Juels said, "It's just nice knowing that there are people like Mark who to crazy extent 140.6 miles to honor her is insane. I'm so honored by him doing this to keep her name alive."

• The logistics of the 13 for 13 Heroes Mission