The U.S. Department of Defense sends another of the emails almost every day. They are lists of air and artillery strikes conducted by the U.S. and coalition forces, ISIS assets targeted, damage and destruction accomplished. On a recent Monday, the tally included 116 ISIS fuel trucks, 11 ISIS tactical units, one large ISIS tactical unit, seven ISIS fighting positions, seven ISIS buildings, one ISIS storage depot, six ISIS vehicles, one ISIS tactical vehicle, one ISIS fighter (he was wounded, the Pentagon said), one ISIS staging area, one ISIS heavy machine gun, one ISIS homemade explosives cache, one ISIS weapons cache, and six ISIS command and control nodes.

The lists, taken on their own, can seem impressive. But they mask the fact that it's still not clear any of this is really accomplishing much.

"The airstrikes, in terms of limiting ISIS' capacity to make advancements in the area it controls, it's probably a C+ or a B-," says Christopher Swift, an adjunct professor of national security studies at Georgetown University. "In terms of forcing ISIS to adapt to a less permissive environment it's probably been a D-."

There have been some successes. Airstrikes have allowed the Iraqi, Syrian rebel, and Kurdish ground forces that the U.S. has allied itself with to capture some territory that had been ISIS'. Earlier this month, Kurdish fighters retook the town of Sinjar in northern Iraq. And days later, the ISIS executioner known as "Jihadi John" was killed in a U.S. drone strike in Syria. Earlier this year, an airstrike reportedly left ISIS' leader, Abu Bakr al-Baghdadi, at least temporarily incapacitated.

But while ISIS' footprint in Iraq and Syria was shrinking, the group's reach was expanding elsewhere. With the attacks ISIS claimed responsibility for in Paris came the message from the group that airstrikes in Syria and Iraq would be met with "the smell of death" at home.

A military aviation specialist who requested anonymity because he isn't authorized to speak on the record told Vocativ that America's air campaign has recently become more effective in part because of the way the administration re-calibrated its assessment of ISIS and its tenacity. When ISIS first appeared on the scene, President Barack Obama dismissed its members as jihadists involved in local power plays — a lesser version of al Qaeda. The early airstrikes on the group reflected that thinking, the specialist said, and that limited their effectiveness.

"For most of those first 15 months the U.S. effort seemed focused on ISIS forces wherever they were found, they were treating almost as independent forces in the field," the specialist said. "It was only recently that you see them operating as though ISIS is a country, going after oil convoys, trying to deprive them of economic support, the same way that the U.S. would be fighting a foreign country."

The targeting of the airstrikes took an even sharper turn after the Russian air force entered the fray in September.

The Russian bombs actually aimed at ISIS, rather than rebels fighting against the regime of Moscow ally President Bashar al-Assad, struck ISIS targets that were relatively "simplistic" in their importance, the specialist said, and U.S. forces "out of opportunity or necessity," were able to refine their selections even more.

When news emerged that the U.S. had shared intelligence with France in the wake of the Paris attacks, giving the French military 20 ISIS-related targets to strike, some observers expressed surprise that the U.S. hadn't eliminated those targets itself.

"There's new threats every day," explained Patrick Skinner, a counter-terrorism expert with The Soufan Group. As new information comes to light, some targets are prioritized over others. Missions change every day as the battleground itself shifts.

As months of the U.S. military campaign in both Iraq and Syria have passed, the U.S. has built partnerships on the ground with Syrian rebels and Kurdish fighters. That's allowed it to increase its knowledge of the battleground and find out more and more about ISIS fighting positions in both countries, and learn the locations and movements of key members.

"It's clear the coalition is getting better intelligence," Skinner said, "but you're not going to win this through air power."

The U.S. military agrees.

"ISIL declared war on humanity 18 months ago," said Col. Steve Warren, the U.S. military spokesman in Baghdad, using another name for ISIS, which is also called the Islamic State. "Airstrikes alone won't defeat them. We need indigenous ground forces too. That combination has liberated Tikrit, Baiji, Sinjar, and has reclaimed a quarter of the territory ISIL once held."

The U.S. has had more success fighting ISIS in Iraq than it has battling it in Syria. There are many reasons for that, but perhaps the most important one is that in Iraq the U.S. has legitimate partners on the ground that it can support from the sky. There's been no such synergy in Syria; Washington has no relationship with Assad, diplomatic, military, or otherwise.

A campaign from the air may eventually grind down ISIS holdings in Syria, but without a resolution to the conflict with Assad the group's defeat may be fleeting. Speaking to reporters in Turkey during the G20 Summit, President Obama said air strikes made up only one component of the U.S. strategy to defeat ISIS.

"Ultimately, to reclaim territory from them is going to require, however, an ending of the Syrian civil war, which is why the diplomatic efforts are so important," Obama told reporters. "And it's going to require an effective Iraqi effort that bridges Shia and Sunni differences, which is why our diplomatic efforts inside of Iraq are so important as well."

This article originally appeared at Have 15 months of U.S. airstrikes hurt ISIS at all?