Clinton rejects claim she's partly to blame for emergence of Isil
Hillary Clinton cast herself as America's strongest leader in a scary world during the second Democratic presidential debate, which was overshadowed by Paris attacks.
But at the event in Des Moines, Iowa, she found herself forced to defend her own role during the rise of the Isil militants.
"This election is not only about electing a president, it's also about choosing our next commander-in-chief," Mrs Clinton said.
"All of the other issues we want to deal with depend upon us being secure and strong."
Amid the backdrop of global anxiety over last Friday's attacks in Paris, Mrs Clinton found herself fending off questions about not only her foreign policy record but her economic ties.
Both Vermont senator Bernie Sanders and former Maryland governor Martin O'Malley painted the former senator from New York as a lackey for Wall Street and corporate interests.
"Let's not be naive about it," said Mr Sanders, noting that Mrs Clinton collected millions in campaign donations from Wall Street bankers.
"They expect to get something. Everybody knows that."
The barbs marked a far more aggressive shift in a primary race that has so far been notable for its civility.
Democrats have spent months boasting about the substantive tone of their contest, attempting to set up a favourable early contrast with the "carnival barker" insults of the crowded Republican race.
Since the Democrats' first debate a month ago, Mrs Clinton has built a lead in the early voting states.
The gains have come amid other signs the party is coalescing behind her, but the nomination fight is far from over.
In Des Moines, Mrs Clinton faced criticism of her national security record.
Mr Sanders traced the current instability in the Middle East to the US Senate's vote - including Mrs Clinton's - to authorise military action in Iraq in 2002.
He said that the US invasion "unravelled the region".
The former secretary of state fought back, saying terrorism has been erupting for decades, specifically mentioning the September 11, 2001, attacks.
She said the recent unrest in Libya and other parts of the Middle East was symptomatic of an "arc of instability from North Africa to Afghanistan".
Mrs Clinton rejected the idea that she and the rest of the Obama administration underestimated the growing threat of Isil.
The row revealed a foreign policy split within the Democratic Party, with Mr Sanders playing to the anti-war activists who boosted then-Illinois senator Barack Obama to victory in 2008.
The Paris attacks seem certain to heighten the importance of foreign policy in an election where it hasn't been prominent. In a recent poll, only 8pc of the public cited terrorism as the most important issue.
"This will help the anti- immigration cause and hurt efforts to bring in Syrian refugees," predicted Vin Weber, a leading Republican strategist.