Not so long ago, ISIS held territory in Syria and Iraq equivalent to the size of the United Kingdom. Yet the U.S. and allied forces have slowly but systematically pried virtually all that real estate from its grip. ISIS will have to change tactics.

A recent article by Michael Dempsey, the former acting director of national intelligence, posited how that may look. ISIS, Dempsey wrote, “is more and more likely to avoid major battlefield engagements and instead resort to terrorist attacks in the Middle East, other conflict zones, and the West.” He suggests we can expect far more suicide bombings and hit-and-run attacks in ISIS’s areas of operation—primarily Iraq, Syria, Afghanistan and the Sinai Peninsula.

On one hand, Dempsey’s hypothesis is likely correct. As long as ISIS wants to keep on fighting —and clearly, it does—it has little choice but to revert to guerilla tactics. However, it would be a mistake to think of this as anything other than a temporary tactical pivot. The terrorist group’s overall strategy will not change. ISIS still aspires to hold territory, govern and ultimately restore a Caliphate—with an appointed caliph—governed by sharia law. This is integral to the raison d’être of not just ISIS but Islamist groups generally.

The creation of a Caliphate is a key tenet of Islamism. In 1938, Hassan el-Banna, the founder of the Muslim Brotherhood, stated that the Brotherhood believed “the caliphate is a symbol of Islamic Union and an indication of the bonds between the nations of Islam.” For that reason, he said, its “re-establishment [was] a top priority.”

A March 2015 piece for The Atlantic by Graeme Wood helped explain the importance of a Caliphate to ISIS and its supporters. He cites a speech delivered in Mosul by Abu Bakr al-Baghdadi just after the public declaration of the Caliphate in June 2014. National barriers would collapse – “Syria is not for the Syrians, and Iraq is not for the Iraqis. The earth is Allah’s” – and a system would be ushered in where “the Arab and the non-Arab, the white man and black man, the easterner and westerner are all brothers”. Al-Baghdadi has stated that the creation of a Caliphate was “a duty upon the Muslims—a duty that has been lost for centuries and absent from the reality of the world and so many Muslims were ignorant of it. The Muslims sin by losing it, and they must always seek to establish it....”

Beyond the political and theological motivations, ISIS has a host of practical reasons for seizing and holding land. Controlling large amounts of territory allows ISIS to create safe havens from which to plan terrorist attacks outside their immediate sphere of influence—such as the ISIS-directed Paris attacks that killed 130 innocents and wounded hundreds more in November 2015.

Moreover, territorial control allows control over people—and not just those already living in the occupied area. The 2014 announcement of a Caliphate led tens of thousands of Muslims to move there. And controlling more territory and people also means a larger cash flow—provided in the 2014-17 Caliphate via taxation, extortion, selling oil, antiquities and the like.

Therefore, ISIS cannot ‘just’ restrict themselves to hit-and-run raids, car bombings and trucks mowing down pedestrians. The need to govern is real.

Dempsey suggests that with the fall of Raqqa and ISIS now less able to direct attacks in the West, there should be more focus on online radicalization. This could involve a “focus on online training for how best to spot the early warning signs of radicalization” and working with private enterprise to promote “alternative content [which] highlights the work of moderate Islamic leaders and skillfully debunks ISIS’ violent narrative and alleged grievances”.

Such initiatives are worth a try, although what constitutes successful counter-messaging is very much open to interpretation. However, the US and its allies cannot lose sight of what is much more tangible: what territory ISIS controls and where. Because while the specific conditions that led to ISIS’s meteoric rise may be hard to replicate, but that does not mean the group has no options. It may be on the back foot in Syria and Iraq, but the political, sectarian and security problems destabilizing both of those countries five years ago—problems that gave ISIS space to operate and succeed—have certainly not been resolved.

Parts of West and North Africa remain vulnerable—none more so than Libya, still gripped in an ongoing struggle for power. At the end of 2016, the Obama administration was so concerned that Sirte, a Libyan city on the Gulf of Sidra, was becoming an ISIS stronghold that it launched a concerted aerial campaign against the group.

Also worth keeping an eye on is the Philippines, where ISIS temporarily held territory and where it continues to have success recruiting.

The U.S. and its allies must remain engaged—be it politically or militarily—in these conflict zones. Should we leave them an opening, ISIS would quickly seek to take advantage of the opportunity to start rebuilding their empire.