2nd Democratic Presidential Debate: 7 Moments That Mattered

— -- Just over a day after a wave of attacks in Paris that claimed the lives of 129 people and injured hundreds of others, the three Democrats running for president sparred over their approaches to confronting the ongoing threat of terrorism.

A large portion of the second Democratic primary debate focused on matters of foreign policy and national security with the candidates offering their takes on the thorny problem of how to combat ISIS.

Clinton, the former secretary of state, who has the most extensive foreign policy record of the three candidates vying for the Democratic nomination, faced pointed questions of her handling of the 2012 terrorist attack in Libya and her 2002 vote in favor of the Iraq war.

Held in the critical early caucus state of Iowa and hosted by CBS News, here are seven moments that mattered at tonight’s debate:

1. Candidates Go to War Over Wall Street

The Democratic presidential debate featured the most heated exchange yet between the candidates over Clinton’s ties to Wall Street.

“Not good enough,” Bernie Sanders said of her promise not to be influenced by Wall Street donors.

“Why over her political career has Wall Street been a major – the major – contributor to Hillary Clinton?”

Clinton said Sanders was looking to “impugn my integrity,” and cast her support for Wall Street as a senator from New York as a way to rebuke terrorists who attacked Lower Manhattan on 9/11.

“It was good for the economy, and it was a way to rebuke the terrorists who had attacked our country,” she said.

She added: “My proposal is tougher, more effective and more comprehensive because I go after all of Wall Street, not just the big banks.”

Martin O’Malley also got in on the action – with economic populism hitting Clinton literally from all sides on stage.

2. Clinton and O’Malley Spar Over ‘American Fight’

With news of the Paris attacks not even 24 hours old, CBS News moderator John Dickerson kicked off the debate with a pointed question for Hillary Clinton: “Won't the legacy of this administration, which you were a part of, won't that legacy be that it underestimated the threat from ISIS?”

Clinton drew contrast with President Obama’s comment Thursday that ISIS had been contained, saying, “It cannot be contained. It must be defeated.”

Clinton then stressed, “This cannot be an American fight, although American leadership is essential.”

But former Maryland Gov. Martin O’Malley said he disagrees with Clinton. “This actually is America's fight,” he said. “It cannot solely be America's fight. America is best when we work in collaboration with our allies,” O’Malley said. “We do have a role in this. Not solely ours, but we must work collaboratively with other nations.”

3. Sanders and Clinton Spat Over Iraq War Vote

A disagreement over a 2002 U.S. Senate vote to invade Iraq came center stage tonight.

“I don't think any sensible person would disagree that the invasion of Iraq led to the massive level of instability we are seeing right now,” said Sanders, who voted against the war in Iraq.

“I think that was one of the worst foreign policy blunders in the modern history of the United States.”

But Clinton responded by listing previous terrorist attacks in the history of the United States.