In the weeks leading up to the election, In Theory is asking policy experts to weigh in on the critical questions our presidential candidates should be addressing — but often aren’t. This week we’re discussing counterterrorism strategies.

Countering ISIS and other terror groups will undoubtedly remain a primary focus for the next president. While both Hillary Clinton and Donald Trump have vowed to fight the Islamic State and dismantle the global terror network, the two presidential candidates have recently accused each other of making the country less secure.

Following a string of attacks last week, Clinton called Trump a “recruiting sergeant for the terrorists,” arguing that his rhetoric on Muslims has become a rallying message for the Islamic State. Trump responded by criticizing President Obama and Clinton for being weak on terrorism and for creating an “extremely open immigration system.”

Political spats aside, what can the next president learn from our decades-long fight against terror around the world? Which strategies have worked, and which haven’t?