As a motley group attempts to retake Mosul from the Islamic State, it behooves America’s presidential candidates to think about how they’d deal with the terrorist group should the push to liberate Iraq’s second-largest city be successful.

Losing Mosul would be a significant blow to the Islamic State. The biggest city under its control, it’s where, over two years ago, the group’s leader, Abu Bakr al-Baghdadi, declared the establishment of an Islamic empire, across Iraq and Syria. Defeat would erode the group’s prestige and its ability to attract new fighters.

However, even if the Islamic State is driven out of Mosul—a likely outcome, though one that won’t come quickly or easily—the group will likely live on as a guerrilla movement like the Taliban, which after losing considerable ground to U.S. forces, is resurgent in Afghanistan. Radical Islamist movements are rarely completely eliminated, as illustrated by al-Qaida in Yemen, al-Shabab in Somalia and Boko Haram in Nigeria.

So far, in fighting the Islamic State, the U.S. has been training local forces and conducting air strikes. Should the battle to retake Mosul go as planned, America ought to scale back its involvement, not ramp it up, which is what both Donald Trump and Hillary Clinton have promised to do.

Trump has grandiosely pledged to “crush and destroy” the Islamic State. Clinton has promised the U.S. will intensify its ground game and aerial assaults.

Fighting guerrillas is much different than fighting regular armies.

Guerrillas, usually inferior to the forces they are fighting, try to isolate small groups of their opponents for ambushes before blending back into the population. They also have time and patience on their side, as demonstrated by the North Vietnamese and Viet Cong, who for decades fought the French, Japanese, and Americans—and their fellow Vietnamese—before finally exhausting them all.

U.S. military and civilian leaders frequently make the mistake of thinking U.S. armed forces will be able to easily vanquish any enemy. But local forces who know an area’s customs, language, politics and economics are generally more effective in battling insurgents, gathering intelligence and winning citizens’ trust. These local forces should be a greater focus of America’s terror-fighting investments.

The candidates have shown little appreciation for these humbling realities.

As this heated campaign reaches its climax, it’d be nice to see the nominees temper their boasts and provide more specific plans for dealing with the Islamic State and the Middle East’s broader unrest. In doing so, Trump and Clinton shouldn’t let election season bombast take America down the wrong road.