Western powers fighting Islamist groups around the globe are condemned to a never-ending battle if they only tackle the symptoms and not the underlying causes of jihadist insurgency, experts say.
"Beyond the tactical victories on the ground, the current strategy is failing," said Katherine Zimmerman, who wrote a recent report for the American Enterprise Institute entitled "Terrorism, Tactics and Transformation: The West vs the Salafi-Jihadi Movement."
"It is easy to say, 'We are going to kill the person responsible for making the bomb.' It is much more difficult to say that our partner government has disenfranchised this group and it is one of the reasons why this person joins the terrorist group. And now he is the bomb maker."
In a report last month on the resurgence of IS as a clandestine guerrilla group, the Center for Strategic and International Studies (CSIS) said that "while the United States and allied governments have weakened some groups like the Islamic State, many of the underlying causes have not been adequately addressed."
At a conference this week in Washington, retired Marine general John Allen -- who once commanded US forces in Afghanistan and now heads the prestigious Brookings Institution -- said the West had to get ahead of the issue and ask, "Where should we be looking for the next problems?"
"Often we join the conversation when the process of radicalisation has been in place for quite a long time."
Allen noted that the problem is "a development issue, much more than a counter-terrorism issue."