With a number of severe terrorist attacks having occurred in the United States, Europe, and around the world in recent years, many Americans are concerned about how to prevent such attacks in the future. Given that the Islamic State in Iraq and Syria (ISIS or ISIL) has carried out, inspired, and claimed responsibility for many of these attacks, the presidential candidates have had to weigh in on what they would do to stop terrorism and defeat ISIS.

Democratic nominee Hillary Clinton has laid out on her website a three-point plan to defeat the radical group.

The first step involves "taking out ISIS's stronghold in Iraq and Syria." To accomplish this, Clinton recommends intensifying the air campaign against ISIS forces and increasing support for local ground troops (like Kurdish pesh merga fighters). She also has expressed openness to increasing the number of Americans deployed to fight ISIS in Iraq (the current level is approximately 5,000). Clinton also stresses the importance of finding a diplomatic solution to the civil war in Syria, which has created the power vacuum that allowed ISIS – with its capital centered in Raqqa, Syria – to take root and thrive.

The second step involves "dismantling the global terror network" by cutting off the flow of money, arms, and fighters that sustain terrorist groups, while also challenging the propaganda that drives recruitment. The third step calls for "hardening our defenses and building our resilience at home." To this end, Clinton wants the private and public sector to collaborate on an "intelligence surge" to track social media posts and chart jihadist networks.

On the whole, Clinton's foreign policy is more "hawkish" and interventionist than Trump's. In Syria, for instance, Clinton not only advocates increasing the bombing campaign but has also endorsed the imposition of a no-fly zone and the ouster, through diplomatic means, of President Assad. Trump, on the other hand, fears getting "bogged down" in a Middle Eastern conflict and is more cautious about intervening in the civil war: having praised the stability caused by dictators like Saddam Hussein, Trump has described any effort to force out Assad while fighting ISIS as "madness and idiocy."

On the whole, Trump has not laid out a comprehensive plan to defeat ISIS, though this may in part be deliberate: in April 2016, Trump said that when it comes to defeating the group, he "won’t tell them where and I won’t tell them how," adding, "We must as a nation be more unpredictable. "

Nevertheless, Trump has proposed some strongly-worded ideas for how to combat ISIS. In March 2016, Trump said that the U.S. had "no choice" but to send 20,000 to 30,000 troops to the region to defeat ISIS. He has also called for the use of torture to obtain counterterrorism information, ordering the military to kill terrorists' families, and the destruction oil assets currently controlled by ISIS. Trump has also floated the idea of threatening other countries with economic sanctions, including U.S. allies like Saudi Arabia, if they do not assist in the fight against ISIS, as well as the prospect of recruiting the security alliance NATO to help take on the Islamic State.

Compared to Clinton and Trump, Libertarian Party nominee Gary Johnson and Green Party nominee Jill Stein have different ideas regarding how to defeat ISIS and protect the country from terrorism.

Both candidates believe that the use of force is counterproductive. Asked whether the U.S. military should be deployed to defeat ISIS, Johnson has said that, "If it involves boots on the ground, if it involves dropping bombs, if it involves flying drones, I think that all those methods have the unintended consequence of making things worse not better.”

Stein has made similar remarks. Calling America's interventionist foreign policy "our own greatest enemy right now," Stein believes that the use of force only creates more violence and drives terrorists' recruitment.

Opposing the deployment of ground troops and the use of aerial bombardment to defeat ISIS, Johnson insists that ruling out these options does not mean "we do nothing." In an article written in November 2015, Johnson laid out several policies for how to stop the group's terrorism.

First, he said, ISIS's finances must be disrupted, and to do this, Johnson recommends that countries cease purchasing oil sold by ISIS. Second, Johnson calls for deploying the country's "formidable technological might" to counter ISIS's online recruitment strategy. Third, Johnson urges the U.S. to assume a larger role in forming strategic partnerships with countries currently battling ISIS and to "galvanize and lead an alliance...that will first contain and ultimately neuter ISIS."

Johnson's running mate Bill Weld has also proposed the creation of a 1,000-member "intelligence task force" comprised of FBI investigators and counterterrorism analysts that would be charged with identifying and rooting out homegrown terrorists.

Stein has proposed a set of similar policies to deprive ISIS of the assets it needs to survive and grow. Writing in March 2016 that the "war on terrorism has catastrophically failed" and that replying to terroristic attacks with violence "is the response the terrorists hope to provoke," Stein recommended a number of ways that the U.S. and countries in the region can starve the group of critical resources.

To deny ISIS income, Stein calls on countries to cease purchasing ISIS's oil and for countries like Saudi Arabia to cease funding the group. To stem the flow of foreign fighters, she wants Turkey to "close its border to the jihadi militias that reinforce them." She also calls on the U.S. to impose a weapons embargo on the Middle East, given that American-delivered arms to countries like Iraq have been captured and used by ISIS.

In short, voters for whom defeating ISIS is a major concern are offered two major agendas by the four leading candidates.

For those who support the use of force, Clinton and Trump are the leading options: Clinton's proposals are a version of the status quo (though, according to one analysis, "just a little bit harder and a little bit faster"), whereas Trump's proposals are in some respects more bellicose (e.g. the deployment of tens of thousands of ground troops to Iraq) and more prudent (e.g. not calling for the abdication of President Assad).

For those opposed to the use of force, Johnson and Stein offer similar ideas: both view the military as exacerbating the problems it is intending to fix and recommend economic and diplomatic solutions to the ISIS threat.