As an 18-year-old military police officer at Guantánamo Bay's prison, Erica Walsh was one of the few women tasked with guarding detainees.

Some were terror suspects linked to the Sept. 11, 2001, attacks - the same attacks that spurred Walsh to enlist. For 12 hours a day, they rained down abuse on her from their cells.

But Walsh, a Montgomery County resident, who admits she cried as a child when she saw roadkill, developed a thick skin and inner strength. Her fortitude grew at similar posts in Iraq and at the maximum security prison at Fort Leavenworth, Kan.

"Being a woman in a man's army, people are constantly nay-saying you," said Walsh, who served for eight years in the Army and now studies health and physical education as a junior at West Chester University. "I want little girls to see they can do anything they want to do."

What she wants to do next is become Ms. Veteran America.

Walsh, 29, is one of about 120 current or former servicewomen nationwide competing in the four-year-old contest, one that celebrates "the woman behind the uniform" and seeks to inspire young women.

Judges score contestants based on grace, poise, confidence, and personality. Winners get a crown, sash, and $15,000, and travel the country for events and community service.

That's where the beauty pageant similarities end.

The competition quizzes women on military history and disregards their height, weight, and age. In 2012, the first year of the contest, an 89-year-old World War II Coast Guard veteran was named second runner-up.

The event "is about service of country and the beauty of that," said Denyse Gordon, who won that year and now serves as competition director.

Walsh gets it. Like other contestants, she's raising money for homeless female veterans - and is about a third of the way toward her $10,000 goal. She also knows her life could have turned out differently if not for her strong support network, including a tight-knit family.

"Things are just too good for me not to do things for other people," she said.

Yet many wouldn't immediately recognize the warrior in the 5-foot-7 woman with sparkling blue eyes and a bright smile.

"When they talk to her and get to know her, they realize she's more than just looks," said her fiance, Dave Webster, a Marine veteran and Philadelphia firefighter.

"She's a lot of brawn," he said, laughing. "She loves that she's a woman and loves what she can do and loves surprising people by that."

Every Memorial Day weekend, Walsh participates in a challenge inspired by a Navy SEAL killed in action, running two miles and completing 100 pull-ups, 200 push-ups, and 300 air squats - all while wearing a 50-pound vest.

Among her goals in the Ms. Veteran America contest is to be named "Push-Up Princess" - the contestant who does the most push-ups in two minutes.

In addition to running her own fitness business and attending college full time, Walsh works as a personal trainer and organizes fund-raisers to help veterans.

So she didn't know at first if she had time to run for Ms. Veteran America when her younger sister, an Army captain, told her about it. The competition's emphasis on advocacy - and the platform the winner gets to promote it - convinced her to enter.

Female veterans are more likely than their male counterparts to raise children alone and to have been victims of sexual trauma in the military - factors that can lead to homelessness, according to the U.S. Department of Veterans Affairs.

More than 4,300 female veterans were homeless last year, according to federal statistics.

The Ms. Veteran America competition also has a special award for entrepreneurship, which Walsh hopes to win for her two-year-old fitness studio, Dub Fitness in King of Prussia. There, she offers free classes to veterans.

Walsh will head to Arlington, Va., in June for the contest's East Coast Regionals. Then the field is narrowed to 25 women for the final competition in Washington in October.

Win or lose, she said, she'll continue to raise money and awareness for her fellow veterans.

"If I don't make it," Walsh said, "I'm not stopping."

610-313-8207@MichaelleBond