"26,000 unreported sexual assaults in the military-only 238 convictions. What did these geniuses expect when they put men & women together?" Trump had tweeted in 2013.
When asked about the tweet by moderator Matt Lauer, Trump didn't back down.
"I think that that's absolutely correct," he said during the forum.
When asked by Lauer if that meant the "only fix is to take women out of the military," Trump said: "No, not to kick them out."
"But something has to happen," he said. "Right now part of the problem is nobody gets prosecuted. You have reported ... you have the report of rape and nobody gets prosecuted."
The issue came up when an audience member asked Trump: "As president, what specifically would you do to support all victims of sexual assault in the military?"
Trump had agreed it's "a massive problem," and something should be done.
"The numbers are staggering, hard to believe it even -- but we're gonna have to run it very tight. I, at the same time, want to keep the court system within the military. I don't think it should be outside of the military," Trump said.
There is an existing military court system, with judges, prosecutors and courts martial, but lawmakers have sought to change the current system to better address sexual assault.