tonight, the question of sexual assault in the military. And a big defeat for the forces trying to change the role commanders play in sexual assault investigations. Kirsten Gillibrand led the charge... See More
tonight, the question of sexual assault in the military. And a big defeat for the forces trying to change the role commanders play in sexual assault investigations. Kirsten Gillibrand led the charge to strip the commanders over their power and give the power to an independent team. What does today's defeat for Hermine for the future? Here's ABC's Cecilia Vega. Reporter: Stacey Thompson wanted so badly to be a marine, she enlisted before she was even 18. That's the thing I'll never forget. I was excited. I wanted to do this. Reporter: But not long after she settled into her first overseas deployment in Japan, she says the nightmare started. Within the first few months, it was sexual harassment. Reporter: The only person she could complain to, was the man who harassed her. The person who sexually harassed you. Sexually harassed me. Reporter: Is the person that you had to make the complaint to? Yes. Reporter: It got worse. My sergeant who was in my direct chain of command, who was my chain of command, ended up raping me that night. Reporter: Thompson and other survivors have taken their fight to Washington. It's not whether anyone in this chamber trusts the chain of command. The people who do not trust the chain of command are the victim ps. Reporter: But today, they were dealt a major blow, when the senate blocked a bill that would have stripped military commanders of their authority to prosecute sex assault cases. And instead, give the power to special military prosecutors. The military's top brass opposed the bill, arguing commanding officers must be allowed to police their own ranks. According to the Pentagon, there were 5,400 reported cases of sexual assault last year. A 60% jump from the year before. And this extraordinary number. 26,000 cases of unwanted sexual contact. Cases that are rarely prosecuted. But the culture of silence slowly being shattered as more survivors speak out. The treatment that I received after that was that it was my fault. If you say something, your career is over. Reporter: As for Stacey Thompson, she is no longer a member of her beloved marine Corps. She says she'll still keep fighting for change. Today's vote was not the final word on military sexual assault. The senate did vote to move ahead on more modest reforms. But Stacey Thompson says more victims will continue to stay in the shadows unless the military's reporting structure changes.
This transcript has been automatically generated and may not be 100% accurate.