Former press secretary Jay Carney's debut Wednesday night as CNN's newest political commentator became a hot topic when he traded words with Sen. John McCain over President Barack Obama's primetime speech on the Islamic State (ISIL).

Carney posited his commentary in support of Obama's strategies in dealing with the ISIL threat. But McCain showed up and criticized his views which compelled the former White House aide to defend himself from a public lashing.

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McCain said he was "astounded" that Carney should claim the Free Syrian Army was stronger.

Carney cut him off, explaining "that's not what I said senator, what I said if I could sir, is we know a great deal more about the makeup of the opposition-"

"Oh come on Jay, we knew all about it then," the Arizona Republican interrupted, adding that Obama had disregarded Washington's security team's recommendation to assist the Free Syrian Army (FSA). He accused Carney of not knowing the facts, stopping short of calling him a liar.

Carney attempted to tone down the exchange, proposing that they could agree to disagree on the issue.

"No, facts are stubborn things," McCain responded.

McCain bashed Obama's unilateral decision to reject his aides' proposal - including the secretary of state - to train and arm the FSA. He went further by directly placing the blame on the president's shoulders when he decided to pull out all of its troops from Iraq.

"The fact that they didn't leave a residual force in Iraq, overruling all of his military advisers is the reason why we're facing ISIS today," McCain said.

"Now the president is saying basically we are going to take certain actions which I would favor. But to say that America is safer and that the situation is very much like Yemen and Somalia shows me the president doesn't have a grasp for how serious the threat of ISIS is," he added.

With regard to the withdrawal of troops in Iraq, Carney explained the deadline for the pull-out was set by the Bush administration, adding that certain protections for American presence in Iraq was not granted by its government.

In response, McCain said Carney, during his time as White House spokesperson, had bragged when the last American troop left Iraq. If a residual force had been left, the threat may not have escalated at this level, he added.

Carney again attempted to steer the conversation to a more diplomatic beat.

While he understood the senator's arguments which were based on facts he believed to be true - case in point, the permission to leave residual troops in Iraq - it was not what the president believed, he said.

"He did what he felt was right for our country," he added.

At one point, Carney appeared as if he had enough but smoothed over his expression and just looked down with a sigh.

Carney was later able to explain his side when he came back after 10 P.M. with Wolf Blitzer.

TagsISIL, ISIS, Jay Carney, John McCain, Barack Obama, Free Syrian Army, terrorist threat, US foreign policy, CNN, Wolf Blitzer