Even as she said that recent history teaches that sending a large American ground force "is just not the smart move," Clinton described a wider and deeper U.S. military commitment alongside a moral and ideological fight against nihilist extremism.
"After a major terrorist attack, every society faces a choice between fear and resolve," Clinton said in a major policy address at the Council on Foreign Relations.
"The world's great democracies can't sacrifice our values or turn our backs on those in need. Therefore, we must choose resolve, and we must lead the world to meet this threat."
Clinton set out a blueprint to combat the Islamic State militants who have taken credit for last week's terror assault in Paris and other recent attacks that demonstrate what Clinton called new reach and ambition to attack Western targets.
The enemy is brutal "jihadism," not Islam, the former secretary of state said, and those who "obsess" over what label to place on the terrorists miss the point, she said.
"An immediate war against an urgent enemy and a generational struggle against an ideology with deep roots will not be easily be torn out," she said. "It will require sustained commitment and every pillar of American power. This is a worldwide fight — and America must lead it."
She was far more clear Thursday that the United States would be in the forefront of the fight than she had been when she addressed the same topic at Saturday night's Democratic debate.
Then, she gave a meandering and widely critiqued answer saying the United States had a responsibility to fight but that the battle "cannot be an American fight."
"We will support those who take the fight to ISIS," she had said at the debate in Iowa.
Now Clinton is making a sharper and more unabashedly hawkish argument that suggests she is looking past her Democratic primary contest with the very liberal Sen. Bernie Sanders (Vt.).
She was harsh and unsparing in criticizing U.S. allies Turkey and Saudi Arabia, along with Qatar and other Gulf Arab states, for facilitating extremism or looking the other way.
"Our efforts will only succeed if the Arabs and Turks step up in a much bigger way," Clinton said. "This is their fight and they need to act like it."
She was toughest on Turkey, a NATO ally. Turkey must finally seal its border with Syria, over which most jihadist recruits cross, and stop bombing Kurdish rebel forces fighting the Islamic State, Clinton said.
Her three-part strategy includes plans to defeat the Islamic State militants who have taken over portions of Syria and Iraq, dismantle the growing terrorist infrastructure that allows the militants to recruit, propagandize and raise money across borders, and harden U.S. and allied defenses.
The plan seeks to highlight Clinton's national security credentials and long experience assembling the kind of international coalitions she said will be required. Her policy prescriptions are more specific than those of either her Democratic or Republican rivals, and they also mark her independence from President Obama’s foreign policy priorities.
"Time is of the essence," said Clinton, who lost an early policy struggle inside the Obama administration about whether to intervene by arming and training Syrian rebels in 2011 and 2012, before the group also known by the acronyms ISIS and ISIL had emerged as a potent threat.
"ISIS is demonstrating new ambition, reach and capabilities. We have to break the group’s momentum and then its back," she said. "Our goal is not to deter or contain ISIS, but to defeat and destroy ISIS."
Clinton’s address follows her pledge during Saturday’s debate to soon expand on her plan to counter the terror network that has claimed responsibility for the attacks in Paris last week that killed more than 120 people.
Republicans have seized on Clinton’s refusal to say that the enemy is “Islamic terrorism,” calling her phrasing at the debate weak. Her primary rivals, Sanders and former Maryland governor Martin O’Malley, also declined to adopt terminology that directly links recent terrorist attacks to Islam.
“Hillary Clinton can’t walk away from President Obama’s failing ISIS strategy because she helped craft it and even praised it," Republican National Committee spokesman Michael Short said, adding that "she’s the wrong person to take on and defeat this growing terrorist threat."
Sanders is also expected to address terrorism and national security in a speech Thursday originally designed to flesh out his political ethos of "Democratic socialism."
Clinton has sought to use the Paris terrorist attacks, as well as recent attacks in Beirut, Nairobi and perhaps Egypt, to highlight foreign policy credentials her rivals do not have.
“This election is not only about electing a president. It's also about choosing our next commander in chief,” Clinton said Saturday.
Clinton, the Democratic front-runner, was already on record supporting a protective “no-fly” zone in Syria, a military undertaking long requested by U.S.-backed rebels fighting both the Islamic State and the regime of Syrian President Bashar al-Assad.
She is alone among the Democratic candidates in calling for a no-fly zone, which she described Thursday as a protective strip in northern Syria, along the Turkish border, where civilians could find refuge. In her most detailed discussion of the proposal, she likened it to the allied no-fly zone in Iraq after the Gulf War and said it would be difficult but "doable" to enforce.
She also prescribed "a more effective coalition air campaign, with more allied planes, more strikes and a broader target set."
The White House she served has resisted a no-fly zone, while Republican presidential candidates such as former Florida governor Jeb Bush and Sen. Marco Rubio of Florida support it.
The Obama administration has edged into greater military involvement since she left office in 2013, approving limited airstrikes against the Islamic State last year and a small number of special operations advisers on the ground this fall.
Clinton has supported those moves as a candidate but went much further Thursday. She conceded during an exchange with moderator Fareed Zakaria that she is advocating an expansion of Obama's policies, but she downplayed the extent of the difference.
"I have made clear that I have differences, as I think any two people do," she said.
But Clinton echoed Obama in defending the resettlement of Syrian war refugees in the United States. Republicans among the 2016 field and in Congress and state houses have sought to bar refugees, at least temporarily, for fear that terrorists might be among them.
"Turning away orphans, applying a religious test, discriminating against Muslims, slamming the door on every single Syrian refugee – that is just not who we are," Clinton said. "We are better than that."
Before the Paris attacks, Clinton had said the United States should vastly expand its Syrian refugee program to bring in 65,000 annually. Obama has set a far more modest goal of 10,000 a year, but even that would be a major change. Only about 2,000 refugees have been resettled in the United States to date, mostly because of stringent vetting and anti-terrorism paperwork requirements.
Officials in at least 30 states have said they would resist any new refugee relocations until adequate safeguards are put in place to screen people for possible terrorist links.
The House is scheduled to vote on legislation Thursday that would block refugees from Syria and Iraq from coming to the United States unless the government can verify that they pose no threat. Obama has threatened to veto such legislation.
The Democratic mayor of Roanoke, Va., David A. Bowers, kicked off a Clinton campaign support committee Wednesday after he invoked the internment of Japanese Americans during World War II as a guide to refusing Syrian refugees now. “Better safe than sorry,” Bowers had said.