President Donald Trump and U.S. officials have described the killing of ISIS leader Abu Bakr al-Baghdadi as a devastating blow to the group and part of its total defeat. But the history of terrorism shows that the demise of extremist groups is rarely that simple.

Counterterrorism is not a chess game that ends when you topple the king. When the leaders of terror groups are captured or killed, it can have a range of effects depending on what extremists believe, how much support they have and how theyre organized. Sometimes terror groups collapse after their leader is gone. But others are resilient and may even increase their attacks.

In the case of the self-described Islamic State, studies suggest the group may persist and regroup without its most successful leader. ISIS has already been able to adapt even as it has drastically declined since its height in 2014, continuing to carry out terror attacks and moving toward guerrilla tactics.

ISIS is actually like the perfect model for building resilience, said Jenna Jordan, an associate professor at Georgia Tech who recently released a book on what happens when terrorist leaders are killed or captured.

There are three key factors in determining what will happen to a terror group after its leader is removed, according to Jordans research, which analyzed over 1,000 examples going back to the early 1970s. These are:

1. The groups level of popular support.

2. Whether its ideology is built to outlast its leader.

3. If the group has a strong bureaucracy and set of institutions to keep things functioning.

When terrorist groups have collapsed after losing a leader, its often been because they scored poorly in those categories. The Japanese doomsday cult Aum Shinrikyo once had tens of thousands of members in multiple countries, for instance, but fell apart after the arrest of its leader Shoko Asahara in 1995, in part because he was so central to the organizations beliefs. The Maoist Peruvian group Shining Path declined following the capture of Abimael Guzman in 1992 as it lost popular support and a charismatic leader.