Pentagon Got ISIS’ Second Ranking Leader. Why We Need to Try Harder.

American defense officials have announced that a very senior Islamic State (ISIS) leader has been killed in a U.S. military operation.

While this is good news, it’s difficult to speculate the exact effect this will have on ISIS’ operations. It’s also pure conjecture to guess at what this success says about the U.S. military’s ability to find and take out other ISIS leadership.

In the war against ISIS, there are only two metrics that will tell whether real progress is being made in taking down ISIS as a global threat.

One, for sure, is getting the self-proclaimed head of the self-proclaimed caliphate, Abu Bakr Baghdadi. This would shake to the core the narrative that ISIS is here to stay.

The second (and more important measure of success) is if ISIS loses its territorial control over Iraq. ISIS’ territory is central to its claim that it’s the beating heart of the global Islamist insurgency. Without it, the group will look like just another dishonored and defeated Islamist wannabe.

Achieving that success will certainly require taking down the black flag in Mosul and the surrounding environs. Iraqi officials have announced the start of a campaign to take back the country’s second largest city. U.S. President Barack Obama has said he would like to see the city liberated before he leaves office—we’ll see.

If ISIS is not driven from the field, the next administration will have to ponder hard what to do next. If ISIS does lose control in Iraq, it will try to regroup in Libya. Al-Qaeda will also try to step up and take leadership of the factions that have sworn allegiance to the black flag.

Either way, there is a long way to go in the long war.