The U.S. air war against the Islamic State, in numbers

This will not be quick," President Obama told reporters at a Monday briefing in the Pentagon, referring to the ongoing U.S. air war against the Islamic State. "This is a long-term campaign. ISIL is opportunistic and it is nimble. . . . It will take time to root them out."

Obama was referring to the acronym used by his administration for the jihadist organization that still controls swaths of territory in Iraq and Syria.

As my colleague Missy Ryan reports, Obama pointed to notable victories enabled by American air strikes:

Obama highlighted battles in which U.S.-aligned fighters have prevailed against the group, including combat in the Syrian cities of Kobane and Tal Abyad and the Iraqi city of Tikrit. He said Islamic State fighters have lost more of than a quarter of the populated territory they had captured in Iraq.

But the jihadists, despite having no state support, remain an entrenched, dogged foe. This a reflection of the particular complexity of the fight. The Obama administration is justifiably keen to limit its role in a yet another conflict Middle East, especially one that has crossed borders and involves coordinating with a mess of factions and state actors on the ground. It's also wary of inflicting civilian casualties.

Micah Zenko, a senior fellow at the Council on Foreign Relations, crunches the numbers of the U.S. air campaign, and sets it against other recent missions. Despite the U.S. air war against the Islamic State now entering a second year, it has conducted far fewer sorties and dropped fewer bombs than during the shock-and-awe campaign in Iraq in 2003 or NATO's operations against Serbian forces in 1999.

Understand that these are all distinct military operations with their own objectives, combination of coalition partners, and rules of engagement, and that this data is challenging to compile. However, for a military campaign that allegedly intends to inflict a “lasting defeat” on the dispersed and large militant army that is the Islamic State, there is a relatively limited — though understandable given the concern of civilian casualties — number of bombs being dropped each day.

Still, according to U.S. estimates, the American bombing campaign has hit nearly 8,000 Islamic State targets and killed some 12,500 Islamic State fighters. It's important to note, as Zenko does, that civilians have still died amid the U.S. air strikes. The Syrian Observatory for Human Rights claims that the U.S.-led coalition is responsible for the deaths of 162 civilians, including 51 children and 35 women.