Democratic Debate
Democratic US presidential candidates Senator Bernie Sanders (L), former Secretary of State Hillary Clinton and former Maryland Governor Martin O'Malley on stage ahead of the second debate in Des Moines, IowaMark Kauzlarich/Reuters

The second Democratic debate in Des Moines, Iowa was recalibrated at the last minute to test the foreign policy skills of the presidential candidates in the wake of the Paris massacre. CBS News, which hosted the debate, sharpened the debate's focus on the battle against terrorism and national security.

Just ahead of the debate, Steve Capus, executive editor of CBS News, sad he had been in the middle of a rehearsal when news of the Paris attacks broke. "American leadership is put to the test. The entire world is looking to the White House. These people are vying to take over this office. This is exactly what the president is going to have to face," said Capus.

The television debate kicked off with a moment of silence for the victims, after which the contenders -- Hillary Clinton, Bernie Sanders and Martin O'Malley -- fought it out over the US's role in the battle against Islamic State (Isis).

Clinton, who served as secretary of state in President Obama's first term, held an advantage over the others on account of her foreign policy experience. She was straightaway asked if the Obama administration had failed in the fight against terrorism. She attempted to sidestep the question, first blaming the Bush administration and then insisting this is not America's fight alone.

The Democratic front-runner, when pressed further, conceded she was in support of arming the moderate Syrian rebels. "We need to understand it and realise that it has antecedents to what happened in Iraq and we have to continue to be vigilant about it," said Clinton.

O'Malley, the former Maryland governor, was asked why he should be given the responsibility of commander-in-chief in the current complex global environment when he has no foreign policy experience. The question clearly took him by surprise, and he avoided answering it altogether. He also disagreed with Clinton saying the US should not take the lead in the fight against terror in the Middle East.

In veiled remarks targeting Clinton, O'Malley said, "Libya is now a mess. Syria is a mess. Iraq is a mess. Afghanistan is a mess. As Americans we have shown ourselves to have the greatest military on the face of the planet but we are not so very good at anticipating threat."

Sanders also did not the miss the opportunity to prick Clinton, pointing out that she had voted in favour of the Iraq War in 2003, which she yet again admitted as a "mistake".

"These toppling of governments, (and) regime changes have unintended consequences. On this issue I'm a little bit more conservative than the secretary and I am not a great fan of regime change," said Sanders.

"I think that was one of the worst foreign policy blunders in the modern history of the United States," he added.

According to a most recent CBS News/New York Times poll, Clinton continues to enjoy 52% support of Democratic voters while Sanders trails with 33% backing. O'Malley, who runs the risk of dropping out from the Democrat race, received just 5% of the vote.