As the all-out offensive against the so-called Islamic State in its Iraqi capital of Mosul began early this week, Pentagon spokesman Peter Cook told reporters, “We will see whether ISIL stands and fights,” as if that were the perfect definition of victory.

But ISIS, as the group is more commonly known, may well have a different plan in mind: the jihadist tactic of hijra.

The word means migration, but for a jihadist it holds significance as a successful retreat and regrouping phase on the way to building a caliphate.

A full decade ago, Mary Habeck, an associate professor of strategic studies at Johns Hopkins University, explained that the jihadists’ war plans mirror the life of the Prophet Muhammad: “First is Mecca: the creation of a vanguard of true believers. Second is Hijra: migration to safety and securing the land. Third is Medina: creating an Islamic state, jihad in the form of both defense and offense, conquest, and winning allies.”

The erstwhile Islamic State of Iraq—the group that became ISIS—used hijra all too successfully. In 2007, the U.S. implemented a troop surge and the Awakening campaign to win over local Iraqis. The jihadists responded by going to other battlefields, including in Syria, only to return in 2014 to claim vast swathes of territory and declare a caliphate—the “Medina” part of picture. So, during or after the battle for Mosul, ISIS is likely to follow the pattern again.

Back in mid-August, American Lt. Gen. Sean MacFarland said, “the enemy is in retreat on all fronts.” But he clarified what this retreat looked like by saying, “All I know is when we go someplace, it’s easier to go there now than it was a year ago. And the enemy doesn’t put up as much of a fight.”

A few weeks earlier, Iraq’s defense minister, Khaled al-Obeidi, also reported that ISIS leaders were evacuating ahead of the Mosul attack. "Many Daesh families and leaders in Mosul have sold their property and sneaked out towards Syria, and a segment even tried to sneak out towards [Iraq's Kurdish] region," he said in an interview on state television.

If the conspiracies of Russian news are to be believed, even more ISIS fighters will be allowed to retreat across the Syrian border during the coming battle because of a supposed under-the-table deal the U.S. made to get them fighting Putin’s forces.

The actual truth probably relates to the border’s unique role in this conflict.

ISIS currently controls a large portion of the Syrian border, which, by its lights, no longer exists. But the border does hem in Iraqi and allied military operations now, as in the past.

Abdel Bari Atwan explains in his book Islamic State: The Digital Caliphate that in the face of U.S.-led bombardment in Iraq in the mid-2000s, ISIS shifted its efforts towards Syria. Fighters in Iraq hid themselves in cities while battalions and sleeper cells in Syria were reactivated. The tactic was a chilling success. “As a result, the group doubled the territory under its control in Syria between August 2014 and January 2015,” Atwan says.

That is why ISIS wants us to call them IS: They ignore borders and exist beyond Iraq and Syria. Atwan points out that in the past, ISIS jihadists have joined the fight in many places, including Afghanistan, Chechnya, Bosnia, and Libya. Their jihad is global and they will make a hijra to wherever there is fighting.

Their military tactics reflect this even on a micro scale, Atwan says: “Rather than fight to the death, [ISIS] brigades will slip away from battles they are clearly not going to win, regrouping in a more advantageous location—a tactic successfully employed for many years by the al Qaeda network.”

The tactic of retreat not only allows ISIS to regroup elsewhere, but it also comes with a heavy price tag for their enemies. Pentagon spokesman and Capt. Jeff Davis says that in the current battle ISIS is "absolutely" using civilians as human shields. "They are being held there against their will," he told Washington reporters on Tuesday. "We have not seen any change in the last day of people leaving or fleeing."

ISIS is, however, retreating from the villages surrounding Mosul. They are leaving behind ransacked houses and an extensive tunnel system. Villagers are trying to salvage their homes in a scene which foreshadows the larger destruction to come. Meanwhile, the tunnel system shows that ISIS has worked carefully to build efficient supply lines while allowing for a safe escape route.

The damage left behind in reclaimed cities has so far been particularly foreboding. Much of Ramadi was completely reduced to rubble, and the Iraqi Prime Minister’s office estimated that 90 percent of the city was contaminated with explosives during the battle. This includes unexploded ordnance from the fighting as well as explosives intentionally placed by ISIS in schools, homes, and hospitals.

A similar pattern occurs whenever a city is reclaimed, making an ISIS retreat very destructive indeed.

Through sabotage and by shielding themselves behind civilians, ISIS is virtually certain to produce a humanitarian disaster in the battle for Mosul. The Iraqi government and its American backers will win a victory (pyrrhic though it may be) because of what Mosul signifies: it is the second largest metropolis in Iraq and was, after all, the place where ISIS leader Abu Bakr al-Baghdadi first declared his caliphate.

It’s not as if the U.S. military does not understand the problem. Lt. Gen. Sean MacFarland said flatly in August, “Military success in Iraq and Syria will not necessarily mean the end of Daesh [ISIS]. We can expect the enemy to adapt, to morph into a true insurgent force and terrorist organization capable of horrific attacks like the one here on July 3 in Baghdad and those others we’ve seen around the world.”

In other words, the jihadists will simply repeat the cycle as they have done in the past. The hijra as a call for jihadists to migrate to the Islamic State will be underway again. If ISIS is indeed prevented from re-entering Iraq, their jihadist fighters will go to other battlefields just as they have in North Africa, the Balkans and Central Asia.

The fight is not against the extremists who hole up in Mosul, finally. This is a war without borders.