Fifth Republican Presidential Debate: 7 Moments That Mattered

— -- Less than 200 miles away from the scene of this month’s ISIS-inspired attack in San Bernardino, California, the nine leading Republican presidential candidates used the final presidential debate of the year to loudly beat the drums of war.

At Tuesday night’s debate, held in Vegas and hosted by CNN, almost every question focused on national security and the fight against Islamic extremism.

“I began this journey six months ago,” frontrunner Donald Trump said. “My total focus was on building up our military, building up our strength."

Meanwhile, Texas Sen. Ted Cruz, rising fast in the polls, doubled down on his call to “carpet bomb ISIS into oblivion,” leaving nothing to the imagination: “What it means is using overwhelming air power to utterly and completely destroy ISIS.”

Former neurosurgeon Ben Carson declared, “we are at war” while former Florida Gov. Jeb Bush took direct aim at president Obama accusing him of “creating the most unstable situation we've had since the World War II era.”

As co-moderator and conservative radio talk show host Hugh Hewitt pointed out, “this will be the debate that Americans talk about at Christmas.” Here are seven moments that mattered at Tuesday’s presidential debate:

1. Jeb Bush and Donald Trump Spar Over Foreign Policy

Right off the bat, the debate kicked off with a focus on Trump’s call to ban Muslims from coming to the United States.

Bush was invited to take the first shot, and started with a fiery quip he surely worked on: “Donald is great at the one-liners. But he’s a chaos candidate. And he’d be a chaos president.”

But Trump didn’t pull any punches. “Jeb doesn't really believe I'm unhinged. He said that very simply because he has failed in this campaign,” he responded. “It's been a total disaster. Nobody cares.”

Later in the debate, the two were at it again, over battling ISIS.

“Are you talking or am I talking, Jeb?” he asked. “I think Jeb is a very nice person. He's a very nice person, but we need tough people.”

But Bush hit back: “Donald, you're not going to be able to insult your way to the presidency. That's not going to happen.”

Later, Trump and Bush took the gloves completely off. “The simple fact is if you think this is tough and you are not being treated fairly, imagine what it will be like dealing with Putin,” Bush said.

“You're a tough guy, Jeb. I know,” Trump said sarcastically, rolling his eyes.

2. Chris Christie Jabs the Senators

Christie always enjoys digging his rivals on the debate stage who are members of the U.S. Senate, jabbing them and boasting about his executive experience. This evening he had a message for the viewers at home:

“If your eyes are glazing over like mine this is what it is like to be on the floor of the United States Senate,” he said. “Endless debates about how many angels on the head of a pin from a person who never had to make a consequential decision in an executive position. For 7 years, I had to make these decisions after 9/11.”

Christie continued, stressing he has the experience to keep the country safe adding he worked with Muslims in New Jersey to get intelligence.

“Let's talk about how we do this and not which bill which these guys like more,” Christie said. “People don't care about that.”

3. Ted Cruz and Marco Rubio Tangle