PARK CITY, Utah » The Department of Defense estimates that more than 19,000 military men and women were sexually assaulted by fellow troops in 2010 while serving in the United States armed forces. At least 20 percent of servicewomen and one percent of men — an estimated 500,000 troops — have experienced sexual trauma while serving.

These troubling statistics motivated documentarian Kirby Dick and producer Amy Ziering to make "The Invisible War," a film that examines the epidemic of rape within the military, how it affects victims and why so few cases are prosecuted. The film premiered at the Sundance Film Festival, where it is a contender in the U.S. documentary competition.

The statistics "were just so astonishing that at first we didn’t believe it," said Dick, adding that he was equally surprised that no film had been made on the subject.

Through interviews with rape survivors and military officials, "The Invisible War" suggests that it’s not just the violence and harassment that traumatizes victims, but the absence of impartial justice and personal retaliation they often experience after reporting the incident. A rape survivor’s only judicial recourse is to report the attack to her commander — even if he was the attacker — and it’s his decision whether to investigate and prosecute, regardless of the evidence.

"If they investigate it, and the investigator comes back and says, ‘I’ve got a slam-dunk case. I can put this serial perpetrator behind bars,’ the commander can, on his or her own, decide no, we’re not going to send this case to court martial," Dick said.

A 2009 study shows that only eight percent of military sex offenders are prosecuted.

"The Invisible War" introduces viewers to Kori Cioca, who left the Coast Guard after being beaten and raped by her supervisor. Five years later, she still suffers from post-traumatic stress and has yet to receive Veterans Administration approval for the surgery she needs to repair the injuries she suffered during the attack. The perpetrator, who continues to serve in the Coast Guard, hit her so hard that he permanently dislocated her jaw.

Viewers also meet Marine Corps 1st Lieutenant Ariana Klay, who served in Iraq before being gang-raped by a senior officer and his friend while stationed at the elite Marine Barracks in Washington, D.C. Klay’s husband, also a Marine, cried as he described his concern and fear that his wife would commit suicide.

Other rape survivors shown in the film, including Cioca, say they also contemplated suicide.

Hannah Sewell, who comes from a military family, said she has trouble convincing herself that she is still a virgin after being raped while serving in the Navy. Her father, wearing his own military uniform, recounts the story through tears.

Dick and Ziering traveled the country to interview some 70 survivors of military rape.

"We weren’t really ready for all the stories we heard," Ziering said. "Each one had a lot of similarities and all were equally horrific."

But the filmmakers say they remained optimistic throughout the project and have been gratified by the film’s reception at Sundance, where politicians such as Sen. Barbara Boxer of California, U.S. Rep. Jackie Speier, Lt. Gov. Gavin Newsom and U.S. Rep. Mike Turner of Ohio attended the premiere. Grammy winner Mary J. Blige has also pledged to write an original song for the film.

"Our great hope was and continues to be that capturing (survivors’) experience and their trauma will help change things for hundreds of thousands of men and women who are in the armed forces," Dick said.

There’s also "a history of hope," he said, because when the military set out to banish the segregation and racism that reigned among troops in the early 1960s, they made significant strides in just over a decade.

"They can do the same thing with this," he said.

So why don’t they?

"They don’t take it seriously enough," Ziering said. "They don’t really see, and what we’re hoping the film will show is the repercussions of it. They don’t understand the amount of damage this is doing and how it really is a national security issue, and also costing taxpayers billions of dollars in just caring for people with this kind of trauma.

"Once that message gets through to them, they will be motivated to make a change, because it’s a no brainer. They have to do something."