Significant international concern that thousands of Islamic State of Iraq and the Levant (ISIL) fighters and their leaders will soon disperse to many countries - once Raqqa and Mosul are liberated - has focused on possible terror threats from a renewed global underground army of frustrated radicals.

This narrow focus will exacerbate the radicalism and terror that have plagued Arab and other countries for decades, for two critical reasons: It neglects the more important underlying drivers of extremism and violence in the Arab world from which both al-Qaeda and ISIL emerged, and it ignores the harsh reality that perhaps tens of millions of ordinary Arab men and women have become ISIL and al-Qaeda sympathisers, which makes it easier for terrorists fleeing Raqqa and Mosul to find refuge and regroup to fight another day.

Concentrating on military attacks against ISIL is sensible to a large extent, but on its own it simply repeats the same mistakes that Middle Eastern and Western leaderships have made for the past 25 years in fighting al-Qaeda and its progeny, ISIL.

Focusing excessively on security responses while reinforcing Arab autocratic regimes ignores the critical political, social, economic, psychological and other factors that must be addressed to truly "defeat" and eliminate those movements.

Millions of sympathisers

Flushing out ISIL from Raqqa and Mosul may even heighten sympathy and practical support for it among ordinary citizens across the Middle East.

The tens of thousands of ISIL fighters and their bureaucratic supporters in the territories that they currently control are a bad enough threat by themselves.

We should focus our attention to a much bigger - and an increasingly clear - reality that perhaps up to 30 or 40 million people across the Arab world express sympathy, support, or approval for ISIL and its actions, based on numerous credible surveys of Arab public opinion.­­­

The Arab world now faces three massive challenges in the post-Raqqa and post-Mosul ISIL era. ­

First, the very large absolute numbers of ISIL "sympathisers"; second, the many reasons for this situation across almost all sectors of society; and third, how the likelihood that both the numbers and the sympathies underpinning ISIL will both increase, if it is dismantled but nothing ­­­is done to improve the degrading conditions that have pushed millions of desperate Arabs to turn to ISIL as a last resort.

Polling and analyses over the past decade show that a steady average of 4 to 10 percent of Arab survey respondents express some degree of understanding, sympathy, or outright support for ISIL and al-Qaeda's activities or motives.

The actual percentage of supporters in some countries reaches up to 40 percent or more in some years, and fluctuates widely, in response to current events usually.

Yet ISIL and al-Qaeda's core support or sympathy among Arabs remains steady in the 4 to 10 percent range mostly.

This means that among the 400 million Arabs today, anywhere between 16 and 40 million people sympathise with ISIL, support its mission or tactics, see its goals or actions as compatible with Islamic principles or, in some other manner, view ISIL positively or with understanding for its aims.

Most ISIL supporters were not motivated by religious sentiments, but rather by political, social, economic and other grievances.

One possibility is that frustrated Arab citizens who express sympathy for ISIL would not actively assist it, but rather they see it as a proxy means of expressing their anger with their own governments and societies, since ISIL directly challenges all ruling Arab power elites.

Even if we cut these figures in half - to be on the safe side - we are still looking at somewhere between eight and 20 million Arabs who view ISIL positively in some manner.

The immediate, frightening aspect about these figures, beyond the core sympathetic base that persists across the region, is that millions of people could make it very easy for ISIL militants who flee Raqqa and Mosul to find refuge in safe places across many Arab lands.

But why?

More problematic are the many underlying reasons why millions of Arabs seem to sympathise with ISIL and al-Qaeda. My own research over the past year into the many causes of Arab discontent indicates as many as 60 distinct reasons why people join, like, or support ISIL.

They can be compartmentalised into five broad categories that affect most citizens: material living standards (housing, income, healthcare, water access, public transportation, etc), human capabilities and opportunities (education, jobs, access to capital), personal freedoms and rights (political participation and accountability, free expression, cultural diversity), reactions to political policies of one's own or aggressive foreign governments, and psychological and personal issues that include positive religious values alongside negative feelings of helplessness, lack of direction, and, ultimately, hopelessness.

The combination of two or more of these conditions tends to drive citizens into the hands of extremists, with the most common sentiment among many who join or like ISIL being a desire to transform their life of vulnerability, humiliation, weakness and suffering into a new life defined by strength, purpose, direction and pride.

An important finding in the 2014 Doha-based Arab Center poll across 12 Arab countries was the lack of any correlation between religiosity and ISIL support; in other words, most ISIL supporters were not motivated by religious sentiments, but rather by political, social, economic and other grievances (PDF).

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Two related points should be emphasised: first, any serious attempt to destroy ISIL or minimise its adherents into insignificance requires a complete understanding of the factors that gave rise to it in the first place; and second, those factors comprise dozens that touch on almost every dimension of life, which means that only comprehensive reforms in the Arab world, alongside military action, can win this war.

This point should be even more evident in view of the global "war on terror", because military attacks did not include improving the underlying conditions that transformed ordinary citizens into desperate terrorists.

These realities are shocking by any standard but, most of all, they should force Arab and foreign political leaders - who now fight ISIL militarily - to also initiate serious reforms of the underlying social, political, economic and other deeply rooted problems in Arab societies that drive ordinary men and women to look kindly on ISIL.

Rami G Khouri is a senior public policy fellow at the Issam Fares Institute at the American University of Beirut and a non-resident senior fellow at Harvard University Kennedy School.

The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.