In this presidential campaign, candidates have often spoken out about their plans to defeat ISIS. Hillary Clinton wants to go after the terrorist group online; Donald Trump went so far as to say he’d declare war if he was elected. But CNN national security analyst Peter Bergen says it’s not that simple.

Even if the U.S. defeated ISIS “tomorrow,” Bergen said during our International News Roundup on July 15, “the essential underlying problems are not going to disappear.”

Those problems, he added, are big challenges that aren’t “susceptible to any easy fixes, not in my professional lifetime.”

Here are what Bergen says are the four root causes of terrorist actions by ISIS—and some context, via our previous coverage.

1. The regional civil war between the Sunni and Shia in Yemen, Iraq and Syria.  We’ve covered the conflict in Syria quite a bit over the last decade, and last month guest host Nia-Malika Henderson and a panel of experts discussed the long-term impact of ISIS’s presence in the Middle East.
2. The collapse of Arab governors across the Middle East. Last year, we spoke to a former foreign correspondent about political corruption’s role in violent extremism.
3. These first two issues have led to a “wave of massive immigration” into Europe, Bergen says. Over the last year, we’ve talked often about Europe’s refugee crisis, from the growing issue to the world’s response, as well as how EU leaders are reacting.
4. The rise of European fascism, which Bergen says is contributing to recent violent terrorist attacks. We looked at the deep-rooted history of the far-right movements and how they are growing in Poland, Germany, France and Hungary, among other European countries.

While there aren’t easy fixes to these issues, there are some way to dampen them, Bergen writes: Institute a no-fly zone in northern Syria, enlist defectors from ISIS to tell their stories publicly, and take out ISIS’ propaganda factories, among others.

Hear more Peter Bergen; find all of our shows on ISIS here.