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Richard Grenell and Matt Littman clashed on "The O'Reilly Factor" tonight while discussing Hillary Clinton's shifting strategy to defeat the Islamic State.

During a speech in New York City today, Clinton reversed course and said that the U.S. must lead the fight against ISIS, after saying at the Democratic debate last weekend that it "cannot be an American fight."

Grenell said that not only is Clinton all over the map, but all of the new policies she proposed during her speech represent failures of the Obama administration. He explained that if she felt to strongly about those plans, then she should have implemented during her tenure as secretary of state.

He also criticized Clinton for declaring that Iran and ISIS are part of the "same challenge."

Littman defended Clinton and the Obama administration's foreign policy by saying that they inherited the Iraq War from President George W. Bush.

"Probably the worst foreign policy of all time," Littman said.

"You don't know what you're talking about," Grenell replied.

Watch the exchange above.

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