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Hagel became one of the Iraq War's fiercest critics in its initial undoings, and he was vehemently opposed to the 2007 troop surge that McCain insists saved the war.
McCain wanted Hagel to give him a direct "yes or no" answer on whether he was wrong about the Iraq surge. Hagel kept trying to delve into a lengthy explanation.
"The question is whether you were right or wrong," McCain said, telling Hagel he "expected a direct answer."
"I'm not going to give you a yes or no answer," Hagel said.
Later, McCain added: "History has already made a judgment about the surge, sir, and you're on the wrong side it."
Here's video of the exchange, via the Washington Free Beacon: