Donald Trump speaks to Matt Lauer during the Commander in Chief Forum in Manhattan, New York, U.S., September 7, 2016. REUTERS/Mike Segar Donald Trump bashed US military leadership during a national-security forum on NBC Wednesday night, saying it has been "reduced to rubble" under President Barack Obama.

The Republican presidential nominee also attacked his Democratic opponent Hillary Clinton, laying blame with the former secretary of state for what he sees as US military failures.

During the forum, NBC host Matt Lauer noted that Trump said he'd always tell people the truth and repeated some of his past statements, including Trump's assertion that he knows "more about ISIS than the generals do."

"Is that the truth?" Lauer asked.

Trump responded that the generals under President Barack Obama and former Secretary of State Hillary Clinton "have not been successful."

Lauer asked if Trump thinks he knows more about ISIS than they do.

"I think under the leadership of Barack Obama and Hillary Clinton, the generals have been reduced to rubble," Trump said. "They have been reduced to a point where it's embarrassing to our country. ... And I can just see the great, as an example, Gen. George Patton spinning in his grave as ISIS, we can't beat."

Lauer asked whether Trump has lost faith in US military commanders.

"I have great faith in the military, I have great faith in certain commanders certainly," Trump said. "But I have no faith in Hillary Clinton or the leadership. ... We need change, Matt. And we have to have it fast."